Re: PyWart: The problem with print
On 4 June 2013 14:35, Mark Lawrence breamore...@yahoo.co.uk wrote: On 04/06/2013 14:29, rusi wrote: The Clash of the Titans Lé jmf chârgeth with mightƴ might And le Mond underneath trembleth Now RR mounts his sturdy steed And the windmill yonder turneth +1 funniest poem of the week :) Week? Do we do this every Tuesday? I vote all-time best post for python-list@python.org. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, Jun 5, 2013 at 10:25 PM, Russ P. russ.paie...@gmail.com wrote: I recall reading a few years ago that Guido was thinking about adding optional type annotations. I don't know if that went anywhere or not, but I thought it was a good idea. Eventually I got tired of waiting, and I realized that I just wanted a statically typed language, so I started using one. Python 3 has support for arbitrary function argument annotations. The language itself ascribes no special meaning to it, so it's up to the user to add a type-checker (or whatever else they might want to use it for). -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, 06 Jun 2013 12:29:44 +1000, Chris Angelico wrote: On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. Whereas people never get confused about the arguments in static typed languages? The only difference is whether the compiler tells you that you've passed the wrong type, or your unit test tells you that you've passed the wrong type. What, you don't have unit tests? Then how do you know that the code does the right thing when passed data of the right type? Adding an extra couple of unit tests is not that big a burden. The valid type(s) for an argument can be divided into two categories: Those the compiler can check for, and those the compiler can't check for. Some languages have more in the first category than others, but what compiler can prove that a string is an HTML-special-characters-escaped string? In a very few languages, the compiler can insist that an integer be between 7 and 30, but there'll always be some things you can't demonstrate with a function signature. That said, though, I do like being able to make at least *some* declaration there. It helps catch certain types of error. *shrug* I don't terribly miss type declarations. Function argument declarations are a bit simpler in Pascal, compared to Python: Function Add(A, B : Integer) : Integer; Begin Add := A + B; End; versus def add(a, b): if not (isinstance(a, int) and isinstance(b, int)): raise TypeError return a + b but not that much simpler. And while Python can trivially support multiple types, Pascal cannot. (Some other static typed languages may.) Whatever benefit there is in declaring the type of a function is lost due to the inability to duck-type or program to an interface. There's no type that says any object with a 'next' method, for example. And having to declare local variables is a PITA with little benefit. Give me a language with type inference, and a nice, easy way to keep duck- typing, and I'll reconsider. But until then, I don't believe the benefit of static types comes even close to paying for the extra effort. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 7:29 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Whatever benefit there is in declaring the type of a function is lost due to the inability to duck-type or program to an interface. There's no type that says any object with a 'next' method, for example. And having to declare local variables is a PITA with little benefit. Give me a language with type inference, and a nice, easy way to keep duck- typing, and I'll reconsider. But until then, I don't believe the benefit of static types comes even close to paying for the extra effort. Here are some classic ways to do the multiple-types-accepted option. //C++ style: overloading int max(int a,int b) {return ab ? a : b;} float max(float a,float b) {return ab ? a : b;} //C++ also lets you go for templates, but leave that aside //Pike style: piped types int|float max(int|float a,int|float b) {return ab ? a : b;} //This lets you write one lot of code but doesn't let //you declare that both args must be the same type # Python style: accept anything, then (maybe) check def max(a,b): return a if ab else b //Pike does this too: mixed max(mixed a,mixed b) {return ab ? a : b;} /* So does C, but only with pointers: */ void *max(void *a,void *b) {... uhh, this is nontrivial actually ...} For the accept any object that has a next() method sorts of rules, I don't know of any really viable system that does that usefully. The concept of implementing interfaces in Java comes close, but the class author has to declare that it's implementing some named interface. In theory there could be something that deduces the validity from the given structure, but I'm not aware of any language that does this. But it would let you do stuff like this (prototyped in Python): class Integers: def __init__(self): self.value=0 def next(self): self.value+=1 return self.value interface Iterable: next(self) def grab_three_values(Iterable iter): return iter.next(),iter.next(),iter.next() With a language that checks these sorts of things at compile time, it's not a big deal to test. With something fully dynamic like Python, it's probably not worth the effort. But maybe checks like this could be useful to something like Coverity. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
06.06.13 12:45, Chris Angelico написав(ла): For the accept any object that has a next() method sorts of rules, I don't know of any really viable system that does that usefully. The concept of implementing interfaces in Java comes close, but the class author has to declare that it's implementing some named interface. In theory there could be something that deduces the validity from the given structure, but I'm not aware of any language that does this. Go? -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 6, 6:45 am, Chris Angelico ros...@gmail.com wrote: On Thu, Jun 6, 2013 at 11:37 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: What prevents bugs is the skill of the people writing the code, not the compiler. +1 QOTW. In many Indian languages there is a saying: A poor dancer blames the crooked floor. [Yeah… sounds tame in English] -- which is probably what Steven is saying. However in defence of the crooked floor… wink When I taught C at the university in the early 90s[1], every third/ fourth compile+run of the kids would result in 'segmentation fault' if they were lucky enough to be on unix, and OS crashes if they were on DOS. At first I would rail at the kids for not doing due diligence. Over time I came to the conclusion that if a system is designed in such a way that everyone is wrong, then its the system that is wrong and not everyone. When we switched from to python (via Scheme and a haskell- predecessor), I dont remember ever getting a segmentation fault. [Well once RR gave some Wx code that I tried and python core dumped. Whether this speaks for RR or Wx or a dangerous combo...] So yes, elegant programming languages are not proof against inelegant programmers. Nevertheless, programming languages can be made in a way that makes certain class of errors harder/easier to make. Joel Spolsky moans that: Java is not, generally, a hard enough programming language that it can be used to discriminate between great programmers and mediocre programmers. http://www.joelonsoftware.com/articles/ThePerilsofJavaSchools.html And Paul Graham is even more provocative: Java programmers are not as smart as python programmers http://www.paulgraham.com/gh.html [1] Prompted a paper in the 90s, with some modernizing modifications http://blog.languager.org/2013/02/c-in-education-and-software-engineering.html -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Fri, Jun 7, 2013 at 12:09 AM, rusi rustompm...@gmail.com wrote: When we switched from to python (via Scheme and a haskell- predecessor), I dont remember ever getting a segmentation fault. Oh, it's easy to segfault Python. import sys sys.setrecursionlimit(9) def foo(): foo() foo() :) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 2013-06-06 10:45, Chris Angelico wrote: For the accept any object that has a next() method sorts of rules, I don't know of any really viable system that does that usefully. The concept of implementing interfaces in Java comes close, but the class author has to declare that it's implementing some named interface. In theory there could be something that deduces the validity from the given structure, but I'm not aware of any language that does this. But it would let you do stuff like this (prototyped in Python): class Integers: def __init__(self): self.value=0 def next(self): self.value+=1 return self.value interface Iterable: next(self) def grab_three_values(Iterable iter): return iter.next(),iter.next(),iter.next() With a language that checks these sorts of things at compile time, it's not a big deal to test. With something fully dynamic like Python, it's probably not worth the effort. But maybe checks like this could be useful to something like Coverity. As Serhiy notes, Go does this, almost exactly as you wrote it (modulo syntax). http://golang.org/doc/effective_go.html#interfaces_and_types -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 6, 8:26 pm, Chris Angelico ros...@gmail.com wrote: On Fri, Jun 7, 2013 at 12:09 AM, rusi rustompm...@gmail.com wrote: When we switched from to python (via Scheme and a haskell- predecessor), I dont remember ever getting a segmentation fault. Oh, it's easy to segfault Python. import sys sys.setrecursionlimit(9) def foo(): foo() foo() :) ChrisA And so you are hereby anointed into the august company of RR!! -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Fri, Jun 7, 2013 at 1:36 AM, rusi rustompm...@gmail.com wrote: On Jun 6, 8:26 pm, Chris Angelico ros...@gmail.com wrote: On Fri, Jun 7, 2013 at 12:09 AM, rusi rustompm...@gmail.com wrote: When we switched from to python (via Scheme and a haskell- predecessor), I dont remember ever getting a segmentation fault. Oh, it's easy to segfault Python. import sys sys.setrecursionlimit(9) def foo(): foo() foo() :) ChrisA And so you are hereby anointed into the august company of RR!! Eh? No, I'm just adept at breaking stuff... I could probably segfault a 100Mbit switch if I tried (or just got careless). ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Fri, Jun 7, 2013 at 1:35 AM, Robert Kern robert.k...@gmail.com wrote: On 2013-06-06 10:45, Chris Angelico wrote: For the accept any object that has a next() method sorts of rules, I don't know of any really viable system that does that usefully. The concept of implementing interfaces in Java comes close, but the class author has to declare that it's implementing some named interface. In theory there could be something that deduces the validity from the given structure, but I'm not aware of any language that does this. But it would let you do stuff like this (prototyped in Python): As Serhiy notes, Go does this, almost exactly as you wrote it (modulo syntax). http://golang.org/doc/effective_go.html#interfaces_and_types Thanks (and thanks for actually providing a link). Many years ago I came to the conclusion that anything I could conceive in language design has already been done somewhere :) Anyway, regardless of your language, there's always some criteria that can't be coded. Suppose the valid input for a function were integers whose square roots are integers but whose cube roots are not. You won't easily get compile-time checking of that. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 11:59:07 AM UTC-5, Chris Angelico wrote: Frankly, I don't think the language much matters. It's all down to the skill of the programmers and testers. Ada wasn't the source of the problem unless Ada has a bug in it... which is going to be true of pretty much any language. Maybe Python would be a better choice, maybe not; but let me tell you this, if the choice of language means the difference between testable in three months and testable code in three years, I'm going for the former. Yes EVEN IF life or property hangs in the balance, the only important decision is how much work YOU will be required to do -- Chris, why i am not amazed by this bombastic display of selfishness? -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Fri, Jun 7, 2013 at 1:49 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: On Wednesday, June 5, 2013 11:59:07 AM UTC-5, Chris Angelico wrote: Frankly, I don't think the language much matters. It's all down to the skill of the programmers and testers. Ada wasn't the source of the problem unless Ada has a bug in it... which is going to be true of pretty much any language. Maybe Python would be a better choice, maybe not; but let me tell you this, if the choice of language means the difference between testable in three months and testable code in three years, I'm going for the former. Yes EVEN IF life or property hangs in the balance, the only important decision is how much work YOU will be required to do -- Chris, why i am not amazed by this bombastic display of selfishness? I would like to say that you're not amazed because you're intelligent enough to understand what I was saying, but I'm not sure it'd be true. Let me spell it out for you. * Deadlines are real things. They make a very audible whooosh as they go past. * If the time frame for developing this is five years, then in five years, the code must either be shipped or scrapped. * Taking three years to get to a testable codebase allows two years to test. * Taking three months to get testable allows over four years to test. Would you say that doubling the testing period is a good thing or a bad thing? ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 2013-06-06 16:41, Chris Angelico wrote: Anyway, regardless of your language, there's always some criteria that can't be coded. Suppose the valid input for a function were integers whose square roots are integers but whose cube roots are not. You won't easily get compile-time checking of that. Say that on a Haskell list, and they'll take it as a challenge. :-) -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 6:18:13 PM UTC-5, Michael Torrie wrote: On 06/05/2013 12:11 AM, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. This comment shows me that you don't understand the difference between names, objects, and variables. May sound like a minor quibble, but there're actually major differences between binding names to objects (which is what python does) and variables (which is what languages like C have). It's very clear Rick does not have an understanding of this either. Just because someone does not prefer this or that aspect of Python, does not mean they don't understand it. I understand implicit conversion to Boolean just fine, however, i don't like it. Actually, i hate it! I think it's foolish. It was invented by people who rather save a few keystrokes at the cost writing cryptic code. There are many good reasons for saving keystrokes, implicit conversion to Boolean is NOT one of them. I make the same argument for return. Some languages allow implicit return values from functions/methods. When writing a function with Ruby, the return statement is optional: ## START RUBY CODE ## def foo: implicit return end rb puts foo implicit return ## END RUBY CODE ## This is one area where Python shines! In Python, if you fail to use the return statement, then Python will return None, NOT some some value that just happens to be the last line executed in the function -- Ruby breaks the law of least astonishment. The point is we must balance our selfish need to save keystrokes against the need of a reader to QUICKLY understand what he is reading. Python's explicit return statement satisfies both requirements, whereas, the optional return value of Ruby does not. We don't want to overly implicit, or overly explicit (as in the nightmare of public static void foo, which is overkill (at least for a language as high level as Python)). -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 12:24 PM, Rick Johnson rantingrickjohn...@gmail.com wrote: In Python, if you fail to use the return statement, then Python will return None, NOT some some value that just happens to be the last line executed in the function -- Ruby breaks the law of least astonishment. Ruby comes from a tradition where this behavior is not astonishing. Languages do not exist in a vacuum. -- Devin -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 2:15:57 AM UTC-5, Chris Angelico wrote: [...] I cannot name a single modern programming language that does NOT have some kind of implicit boolification. Congrats: Again you join the ranks of most children who make excuses for their foolish actions along the lines of: Hey, they did it first! Well, the lemmings get what they deserve i suppose. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Fri, Jun 7, 2013 at 2:49 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: On Wednesday, June 5, 2013 2:15:57 AM UTC-5, Chris Angelico wrote: [...] I cannot name a single modern programming language that does NOT have some kind of implicit boolification. Congrats: Again you join the ranks of most children who make excuses for their foolish actions along the lines of: Hey, they did it first! Well, the lemmings get what they deserve i suppose. You say that like it's a bad thing. http://www.catb.org/jargon/html/E/ELIZA-effect.html ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 6, 9:08 pm, Robert Kern robert.k...@gmail.com wrote: On 2013-06-06 16:41, Chris Angelico wrote: Anyway, regardless of your language, there's always some criteria that can't be coded. Suppose the valid input for a function were integers whose square roots are integers but whose cube roots are not. You won't easily get compile-time checking of that. Say that on a Haskell list, and they'll take it as a challenge. :-) Yes, all programming communities have blind-spots. The Haskell community's is that Haskell is safe and safe means that errors are caught at compile-time. Unfortunately* the halting problem stands. When generalized to Rice theorem it says that only trivial properties of programs are algorithmically decidable: http://mathworld.wolfram.com/RicesTheorem.html And so the semantic correctness of a program -- a non-trivial property -- is not decidable. In short the Haskell dream is a pipe-dream**. Discussed in more detail here: http://blog.languager.org/2012/08/functional-programming-philosophical.html. Nevertheless I need to say: If a programmers comes to python from Haskell, he will end up being a better programmer than one coming from C or Java or… * actually fortunately considering that for most of us programming is our job :-) ** Haskellers would point out that there is agda which grows out of Haskell and in agda one can encode arbitrary properties of types. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 2013-06-06, Chris Angelico ros...@gmail.com wrote: Would you say that doubling the testing period is a good thing or a bad thing? It could be a neutral thing (ignoring the costs involved). I once read read an article claiming that as you test (and fix) any large, complex piece of software, you asymptotically approach a certain fixed minimum number of bugs that's determined by the system's overall architecture, design and implentation. Once you get sufficiently close to that minimum, additional testing doesn't reduce the number/severity of bugs -- it just moves them around by creating additional bugs at the same rate you are eliminating old ones. When you get to that point, the only way to significantly improve the situation is to toss the whole thing out and start over with a better system architecture and/or development model. After having maintined a few largish pieces of software for well over a decade, I'm fairly convinced that's true -- especially if you also consider post-deployment maintenance (since at that point you're usually also trying to add features at the same time you're fixing bugs). -- Grant Edwards grant.b.edwardsYow! I just went below the at poverty line! gmail.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
Whatever benefit there is in declaring the type of a function is lost due to the inability to duck-type or program to an interface. There's no type that says any object with a 'next' method, for example. And having to declare local variables is a PITA with little benefit. Give me a language with type inference, and a nice, easy way to keep duck- typing, and I'll reconsider. But until then, I don't believe the benefit of static types comes even close to paying for the extra effort. Okay, I'm going straighten out you foo(l)s once and for all. Python has seduced us all into lazy typing. That's what it is. Manual type checking is obviously inferior to compiler type-checking. This is what I was trying to tell you all with the post of re-vamping the Object model. Python, and I along with it, went towards this idea of a grand god Object that is the father of everything, but it turned out to be the wrong direction. Refer to my post on OOPv2. The fact is, that none of us is close enough to God and the programming art isn't evolved enough to try to accomplish some grand generic object at the top of the ObjectModel. It just isn't. We were better off closer to the machine. Automatic conversion from int to long was good enough. -- MarkJ Tacoma, Washington P.S. See also PythonThreeThousand on wikiwikiweb http://c2.com/cgi/wiki?WikiWikiWeb -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 8:37:20 PM UTC-5, Steven D'Aprano wrote: On Wed, 05 Jun 2013 09:15:01 -0700, Russ P. wrote: On Wednesday, June 5, 2013 1:59:01 AM UTC-7, Mark Lawrence wrote: On 05/06/2013 07:11, Russ P. wrote: What prevents bugs is the skill of the people writing the code, not the compiler. Compile-time static type checking is merely a tool, which has costs and benefits. It is ludicrous to think that any one single tool, or the lack of that tool, will make all the difference between working code and non-working code. Yes, just as ludicrous as thinking that dynamic languages have abolished the evil practice of type checking. Static type-checking is no better, or worse, for critical code than dynamic type-checking. One language chooses to deal with some errors at compile-time, others deal with them at run-time. Wow, talk about ignoring the elephant in the room! I don't feel i need static typed languages for EVERY problem, however, i'm not foolish enough to believe that compile time type checking and run-time type checking are even comparable. Oversimplification? Either way, the programmer has to deal with them in some way. A static type system forces you to deal with a limited subset of errors, type errors, in one way only: by removing any execution paths in the software which would assign data of type X to a variable of type Y. For reasons of machine efficiency, that is often a good was to deal with such errors. But a dynamic type system makes different trade-offs. And of course, type errors are such a vanishingly small subset of all the possible errors that might be made that, frankly, the difference in code quality between those with static typing and those without is essentially indistinguishable. There's no evidence that code written in static typed languages is less buggy than code written in dynamic languages. WOW! Your skill with the implicit Ad hominem is approaching guru status. First you cleverly convert the base argument of this ongoing discussion from: implicit conversion to boolean is bad, into the hot button topic of: static vs dynamic typing. In this manner you can ratchet up the emotion of your supporters by employing the same political slight of hand used by countless political hacks: Liberal vs Republican ring a bell? When there is only two choices, the sheeple can be easily manipulated by the football game. Especially when the opposing sides have the same end-goal in mind. It's all a game of diversions you idiots! Then you go and make a blanket statement that appears to weigh the differences of the two styles fairly, when in fact, what you've done is to falsely invalidate the opposition's entire argument based on a complete overstatement (not to mention that you stopped short of explaining the trade offs in detail): And of course, type errors are such a vanishingly small subset of all the possible errors that might be made that, frankly, the difference in code quality between those with static typing and those without is essentially indistinguishable. Nice! Well, then. You've slayed the enemy. If type errors are as rare as you claim, then by golly these crazy people who use static languages are really just fools. I mean, how could they not be? If they were as intelligent as YOU then they would see the truth! Your attempts at sleight of hand are rather amusing. The whole point of this implicit conversion to Boolean discussion hinges around the fact that dynamic languages are okay for small to medium problems ( or for prototyping larger problems). But they cannot be depended on for mission critical code. And mission critical does not only encompass manned flights to mars, it could be any code that places your reputation on the line. I don't want Python to be a static typed language. Neither do i believe that duck typing is wrong for Python. HOWEVER, what i DO believe is that dynamic languages can be unreliable if we do not: 1. Choose to be explicit enough I've explained this in detail Ad-nauseam. 2. Fail to type check where type checking is due. The second covers type checking objects that enter into new namespaces. That would cover all functions/methods arguments (at a minimum). We don't need to type check EVERY single object (but of course the programmer could IF he wanted to). If i declare a variable[1] that points to a list in a block of code, then i reference that variable[1] in the same block of code, i see no reason to type check that variable[1] first. That is overkill and that is why people are turned off by static languages. However, if i declare the same variable[1] and then pass that variable[1] into a function, the function should do a type check on all the arguments to guarantee that these arguments are in fact what they should be. This is how you strike a balance between explicit and implicit. This is how you inject sanity into your code
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thursday, June 6, 2013 2:29:02 AM UTC-7, Steven D'Aprano wrote: On Thu, 06 Jun 2013 12:29:44 +1000, Chris Angelico wrote: On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. Whereas people never get confused about the arguments in static typed languages? The only difference is whether the compiler tells you that you've passed the wrong type, or your unit test tells you that you've passed the wrong type. What, you don't have unit tests? Then how do you know that the code does the right thing when passed data of the right type? Adding an extra couple of unit tests is not that big a burden. The valid type(s) for an argument can be divided into two categories: Those the compiler can check for, and those the compiler can't check for. Some languages have more in the first category than others, but what compiler can prove that a string is an HTML-special-characters-escaped string? In a very few languages, the compiler can insist that an integer be between 7 and 30, but there'll always be some things you can't demonstrate with a function signature. That said, though, I do like being able to make at least *some* declaration there. It helps catch certain types of error. *shrug* I don't terribly miss type declarations. Function argument declarations are a bit simpler in Pascal, compared to Python: Function Add(A, B : Integer) : Integer; Begin Add := A + B; End; versus def add(a, b): if not (isinstance(a, int) and isinstance(b, int)): raise TypeError return a + b Scala also has isInstanceOf[Type] which allows you to do this sort of thing, but of course it would be considered terrible style in Scala. but not that much simpler. And while Python can trivially support multiple types, Pascal cannot. (Some other static typed languages may.) Whatever benefit there is in declaring the type of a function is lost due to the inability to duck-type or program to an interface. There's no type that says any object with a 'next' method, for example. And having to declare local variables is a PITA with little benefit. Give me a language with type inference, and a nice, easy way to keep duck- typing, and I'll reconsider. But until then, I don't believe the benefit of static types comes even close to paying for the extra effort. Scala has type inference. For example, you can write val x = 1 and the compiler figures out that x is an integer. Scala also has something called structural typing, which I think is more or less equivalent to duck typing, although I don't think it is used very often. Are you ready to try Scala yet? 8-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thursday, June 6, 2013 1:03:24 PM UTC-5, Rick Johnson wrote: The second covers type checking objects that enter into new namespaces. That would cover all functions/methods arguments (at a minimum). Yeah, before anyone starts complaining about this, i meant to say scope. Now you can focus on the *real* argument instead of spending all your time pointing out minutiae. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
Super OT divergence because I am a loser nerd: On Thu, Jun 6, 2013 at 1:27 PM, rusi rustompm...@gmail.com wrote: Yes, all programming communities have blind-spots. The Haskell community's is that Haskell is safe and safe means that errors are caught at compile-time. I don't think Haskell people believe this with the thoroughness you describe. There are certainly haskell programmers that are aware of basic theory of computation. Unfortunately* the halting problem stands. When generalized to Rice theorem it says that only trivial properties of programs are algorithmically decidable: http://mathworld.wolfram.com/RicesTheorem.html And so the semantic correctness of a program -- a non-trivial property -- is not decidable. Just because a problem is NP-complete or undecidable, doesn't mean there aren't techniques that give the benefits you want (decidability, poly-time) for a related problem. Programmers often only or mostly care about that related problem, so it isn't the end of the line just when we hit this stumbling block. As far as undecidability goes, one possibility is to accept a subset of desired programs. For example, restrict the language to not be turing complete, and there is no problem. Another resolution to the problem of undecidability is to accept a _superset_ of the collection you want. This permits some programs without the property we want, but it's often acceptable anyway. A third approach is to attach proofs, and only accept a program with an attached and correct proof of said property. This is a huge concept, vital to understanding complexity theory. It may be undecidable to find a proof, but once it is found, it is decidable to check the proof against the program. Haskell takes something akin to the second approach, and allows errors to exist which would require too much work to eliminate at compile time. (Although the type system is a literal case of the first resolution). Python, by contrast, often values flexibility over correctness, regardless of how easy it might be to check an error at compile time. The two languages have different philosophies, and that is something to respect. The reduction to Rice's theorem does not respect the trade-off that Haskell is making, it ignores it. It may be a pipe dream to get everything ever, but that's not to say that the entire approach is invalid and that we should ignore how Haskell informs the PL discourse. For some reason both the Python and Haskell communities feel the other is foolish and ignorant, dismissing their opinions as unimportant babbling. I wish that would stop. -- Devin -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 7, 3:59 am, Mark Janssen dreamingforw...@gmail.com wrote: Okay, I'm going straighten out you foo(l)s once and for all. Gosh, really?! THANKS. Python has seduced us all into lazy typing. That's what it is. Bulshytt. If you have no idea what polymorphism is, you shouldn't even be participating in this conversation. The fact is, that none of us is close enough to God More bulshytt. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 7, 2:39 am, Devin Jeanpierre jeanpierr...@gmail.com wrote: Languages do not exist in a vacuum. They do if all you use them for is academic point scoring over practical purposes. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 9:49 AM, Rick Johnson rantingrickjohn...@gmail.comwrote: Congrats: Again you join the ranks of most children who make excuses for their foolish actions along the lines of: Hey, they did it first! Well, the lemmings get what they deserve i suppose. Lemmings don't really jump off cliffs. The Disney film documenting it was staged by a film crew who'd -heard- Lemmings did, and forced the little guys over a cliff in the name of saving time. http://en.wikipedia.org/wiki/Lemming -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
Python has seduced us all into lazy typing. That's what it is. Bulshytt. If you have no idea what polymorphism is, you shouldn't even be participating in this conversation. I am aware of what it means, but Python doesn't really have it (although it may evolve to it with annotations). But then these debates were over a decade ago. MarkJ Tacoma, Washington -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 7, 11:44 am, Mark Janssen dreamingforw...@gmail.com wrote: Bulshytt. If you have no idea what polymorphism is, you shouldn't even be participating in this conversation. I am aware of what it means, but Python doesn't really have it You really need to stop commenting when you clearly have no understanding of what you're talking about. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, 06 Jun 2013 18:44:49 -0700, Mark Janssen wrote: Python has seduced us all into lazy typing. That's what it is. Bulshytt. If you have no idea what polymorphism is, you shouldn't even be participating in this conversation. I am aware of what it means, but Python doesn't really have it (although it may evolve to it with annotations). No polymorphism huh? py len([1, 2, 3]) # len works on lists 3 py len((1, 2)) # and on tuples 2 py len({}) # and on dicts 0 py len('I pity the fool') # and on strings 15 py len(b'\x23') # and on bytes 1 py len(set(range(2))) # and on sets 2 py len(frozenset(range(4))) # and on frozensets 4 py len(range(1000)) # and on range objects 1000 Looks pretty polymorphic to me. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 6, 11:44 pm, Devin Jeanpierre jeanpierr...@gmail.com wrote: Unfortunately* the halting problem stands. When generalized to Rice theorem it says that only trivial properties of programs are algorithmically decidable: http://mathworld.wolfram.com/RicesTheorem.html And so the semantic correctness of a program -- a non-trivial property -- is not decidable. Just because a problem is NP-complete or undecidable, doesn't mean there aren't techniques that give the benefits you want (decidability, poly-time) for a related problem. Programmers often only or mostly care about that related problem, so it isn't the end of the line just when we hit this stumbling block. As far as undecidability goes, one possibility is to accept a subset of desired programs. For example, restrict the language to not be turing complete, and there is no problem. Another resolution to the problem of undecidability is to accept a _superset_ of the collection you want. This permits some programs without the property we want, but it's often acceptable anyway. A third approach is to attach proofs, and only accept a program with an attached and correct proof of said property. This is a huge concept, vital to understanding complexity theory. It may be undecidable to find a proof, but once it is found, it is decidable to check the proof against the program. Haskell takes something akin to the second approach, and allows errors to exist which would require too much work to eliminate at compile time. (Although the type system is a literal case of the first resolution). Python, by contrast, often values flexibility over correctness, regardless of how easy it might be to check an error at compile time. The two languages have different philosophies, and that is something to respect. The reduction to Rice's theorem does not respect the trade-off that Haskell is making, it ignores it. It may be a pipe dream to get everything ever, but that's not to say that the entire approach is invalid and that we should ignore how Haskell informs the PL discourse. Nice 3-point summary. Could serve as a good antidote to some of the cargo-culting that goes on under Haskell. To make it very clear: In any science, when there are few people they probably understand the science. When the numbers explode, cargo-cult science happens. This does not change the fact that a few do still understand. Haskell is not exception. See below On Thu, Jun 6, 2013 at 1:27 PM, rusi rustompm...@gmail.com wrote: Yes, all programming communities have blind-spots. The Haskell community's is that Haskell is safe and safe means that errors are caught at compile-time. I don't think Haskell people believe this with the thoroughness you describe. There are certainly haskell programmers that are aware of basic theory of computation. Of course! Here's cmccann from Haskell weekly news of May 31: [On reimplementing cryptography in pure Haskell] writing in Haskell lets you use type safety to ensure that all the security holes you create are subtle instead of obvious. Which is showing as parody exactly what I am talking of: All errors cannot be removed algorithmically/mechanically. And here's Bob Harper -- father of SML -- pointing out well-known and less well-known safety problems with Haskell: http://existentialtype.wordpress.com/2012/08/14/haskell-is-exceptionally-unsafe/ -- Super OT divergence because I am a loser nerd: Uh? Not sure I understand… OT: OK: How can you do programming if you dont understand it? I guess in a world where majority do it without understanding, someone who understands (more) will be called 'nerd'? For some reason both the Python and Haskell communities feel the other is foolish and ignorant, dismissing their opinions as unimportant babbling. I wish that would stop. Dunno whether you are addressing me specifically or python folks generally. If me, please remember my post ended with If a programmer comes to python from Haskell, he will end up being a better programmer than one coming from C or Java or… If addressed generally, I heartily agree. My proposed course: https://moocfellowship.org/submissions/the-dance-of-functional-programming-languaging-with-haskell-and-python is in this direction. That is it attempts to create a new generation of programmers who will be able to use Haskell's theory-power to pack an extra punch into batteries-included python. More details: http://blog.languager.org/2013/05/dance-of-functional-programming.html -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
I am aware of what it means, but Python doesn't really have it (although it may evolve to it with annotations). No polymorphism huh? py len([1, 2, 3]) # len works on lists 3 py len((1, 2)) # and on tuples 2 py len({}) # and on dicts 0 py len('I pity the fool') # and on strings 15 py len(b'\x23') # and on bytes 1 py len(set(range(2))) # and on sets 2 py len(frozenset(range(4))) # and on frozensets 4 py len(range(1000)) # and on range objects 1000 Okay, wow, it looks like we need to define some new computer science terms here. You are making an outside view of a function (until a better term is found). So that give you one possible view of polymorphism. However, *within* a class that I would write, you would not see polymorphism like you have in C++, where it is within the *function closure* itself. Instead you would see many if/then combinations to define the behavior given several input types. I would call this simulated polymorphism. But don't quote me on this because I have to review my 20 years of CS and see if it matches what the field says -- if the field has settled on a definition. If not, I go with the C++ definition, and there it is very different than python. But then, you weren't going to quote me anyway, right? -- MarkJ Tacoma, Washington -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 7, 8:14 am, Mark Janssen dreamingforw...@gmail.com wrote: I am aware of what it means, but Python doesn't really have it (although it may evolve to it with annotations). No polymorphism huh? py len([1, 2, 3]) # len works on lists 3 py len((1, 2)) # and on tuples 2 py len({}) # and on dicts 0 py len('I pity the fool') # and on strings 15 py len(b'\x23') # and on bytes 1 py len(set(range(2))) # and on sets 2 py len(frozenset(range(4))) # and on frozensets 4 py len(range(1000)) # and on range objects 1000 Okay, wow, it looks like we need to define some new computer science terms here. Fairly definitive terms have existed since 1985: http://lucacardelli.name/Papers/OnUnderstanding.A4.pdf You are making an outside view of a function (until a better term is found). So that give you one possible view of polymorphism. However, *within* a class that I would write, you would not see polymorphism like you have in C++, where it is within the *function closure* itself. Instead you would see many if/then combinations to define the behavior given several input types. I would call this simulated polymorphism. Cardelli and Wegner cited above call this ad-hoc polymorphism. What you are calling polymorphism, they call universal polymorphism. See sect 1.3 for a summary diagram -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
Fairly definitive terms have existed since 1985: http://lucacardelli.name/Papers/OnUnderstanding.A4.pdf You are making an outside view of a function (until a better term is found). So that give you one possible view of polymorphism. However, *within* a class that I would write, you would not see polymorphism like you have in C++, where it is within the *function closure* itself. Instead you would see many if/then combinations to define the behavior given several input types. I would call this simulated polymorphism. Cardelli and Wegner cited above call this ad-hoc polymorphism. What you are calling polymorphism, they call universal polymorphism. Okay, THANK YOU for the reference. The main thing to note is that there is a difference. Those terms sound good enough. -- MarkJ Tacoma, Washington -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 7, 8:24 am, rusi rustompm...@gmail.com wrote: On Jun 7, 8:14 am, Mark Janssen dreamingforw...@gmail.com wrote: I am aware of what it means, but Python doesn't really have it (although it may evolve to it with annotations). No polymorphism huh? py len([1, 2, 3]) # len works on lists 3 py len((1, 2)) # and on tuples 2 py len({}) # and on dicts 0 py len('I pity the fool') # and on strings 15 py len(b'\x23') # and on bytes 1 py len(set(range(2))) # and on sets 2 py len(frozenset(range(4))) # and on frozensets 4 py len(range(1000)) # and on range objects 1000 Okay, wow, it looks like we need to define some new computer science terms here. Fairly definitive terms have existed since 1985:http://lucacardelli.name/Papers/OnUnderstanding.A4.pdf You are making an outside view of a function (until a better term is found). So that give you one possible view of polymorphism. However, *within* a class that I would write, you would not see polymorphism like you have in C++, where it is within the *function closure* itself. Instead you would see many if/then combinations to define the behavior given several input types. I would call this simulated polymorphism. Cardelli and Wegner cited above call this ad-hoc polymorphism. What you are calling polymorphism, they call universal polymorphism. See sect 1.3 for a summary diagram I should have added that python has the universal polymorphism that you want: $ python Python 2.7.5 (default, May 20 2013, 13:49:25) [GCC 4.7.3] on linux2 Type help, copyright, credits or license for more information. len([1,2]) 2 len([[1,2]]) 1 len([[[1,2]],[[3]],[[4,5]]]) 3 The main thing to note about universal - parametric polymorphism is that one definition works for an infinite set of types, without any extra code(ing) -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 6/6/13, alex23 wuwe...@gmail.com wrote: On Jun 7, 11:44 am, Mark Janssen dreamingforw...@gmail.com wrote: Bulshytt. If you have no idea what polymorphism is, you shouldn't even be participating in this conversation. I am aware of what it means, but Python doesn't really have it You really need to stop commenting when you clearly have no understanding of what you're talking about. Clearly, okay. You've added a wee bit of constructive argument *if* you're considered reputable to the rest of the list; however, polymorophism, should really only be considered true when specifically in a functional enclosure. C++ has this, through it's type system, more strictly when there is no references to variables outside the function scope. Python does not. But this all relates to theoretical ObjectArchitecture and ModelsOfComputation that aren't well-understood outside a few specialized folks. Good luck trying to work through the chaff, if you don't want to know the difference. -- MarkJ Tacoma, Washington -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Tuesday, June 4, 2013 8:44:11 AM UTC-7, Rick Johnson wrote: Yes, but the problem is not my approach, rather the lack of proper language design (my apologizes to the anointed one. ;-) If you don't like implicit conversion to Boolean, then maybe you should be using another language -- and I mean that in a constructive sense. I'm not particularly fond of it either, but I switched from Python to another language a while back. The issue is not a lack of proper language design but rather a language design philosophy that values conciseness and simplicity over explicitness and rigor. Implicit conversion to Boolean is only one of many language features that are questionable for critical production software. Another is the convention of interpreting negative indices as counting backward from the end of a list or sequence. Yeah, I thought that was elegant... until it bit me. Is it a bad idea? Not necessarily. It certainly enhances programmer productivity, and it can be done correctly almost all the time. But that one time in a hundred or a thousand when you accidentally use a negative index can be a bitch. But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, Jun 5, 2013 at 4:11 PM, Russ P. russ.paie...@gmail.com wrote: On Tuesday, June 4, 2013 8:44:11 AM UTC-7, Rick Johnson wrote: Yes, but the problem is not my approach, rather the lack of proper language design (my apologizes to the anointed one. ;-) If you don't like implicit conversion to Boolean, then maybe you should be using another language -- and I mean that in a constructive sense. I'm not particularly fond of it either, but I switched from Python to another language a while back. The issue is not a lack of proper language design but rather a language design philosophy that values conciseness and simplicity over explicitness and rigor. (Out of curiosity, which language? Feel free to not answer, or to answer off-list, as that's probably not constructive to the thread.) I cannot name a single modern programming language that does NOT have some kind of implicit boolification. The only such language I know of is REXX, which has a single data type for everything, but insists on the exact strings 1 and 0 for True and False, anything else is an error. Every other language has some definition of these things are true, these are false; for instance: * C-family languages treat all nonzero integers as true * Shells treat 0 as success and nonzero as error, and therefore as true and false respectively (yes, this IS an inversion) * Pike allows any variable to contain the integer 0, regardless of its declared type, and thus is a sort of null value which is false; all strings, arrays, mappings, etc are true * Python treats an empty thing as false and a nonempty one as true SQL is like REXX in that it's fairly strict; a condition must be a boolean (example from PostgreSQL): rosuav= select 1+2 where 1; ERROR: argument of WHERE must be type boolean, not type integer LINE 1: select 1+2 where 1; ^ But an explicit conversion is permitted: rosuav= select 1+2 where cast (5 as boolean); ?column? -- 3 (1 row) It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. The looseness doesn't preclude critical applications. It's all a question of what you're testing. Does your code care that this be a list, and not something else? Then test! You have that option. What happens if it isn't a list, and something is done that bombs with an exception? Maybe that's not a problem. Critical applications can often be built in layers. For instance, a network server might listen for multiple socket connections, and for each connection, process multiple requests. You would want to catch exceptions at the two boundaries there; if a request handler crashes, the connection should not be dropped, and if a connection handler crashes, the server should keep running. With some basic defenses like that, your code need no longer concern itself with trivialities - if something goes wrong, there'll be an exception in the log. (BTW, this is one of the places where a bare or very wide except clause is appropriate. Log and move on.) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 12:15:57 AM UTC-7, Chris Angelico wrote: On Wed, Jun 5, 2013 at 4:11 PM, Russ P. wrote: On Tuesday, June 4, 2013 8:44:11 AM UTC-7, Rick Johnson wrote: Yes, but the problem is not my approach, rather the lack of proper language design (my apologizes to the anointed one. ;-) If you don't like implicit conversion to Boolean, then maybe you should be using another language -- and I mean that in a constructive sense. I'm not particularly fond of it either, but I switched from Python to another language a while back. The issue is not a lack of proper language design but rather a language design philosophy that values conciseness and simplicity over explicitness and rigor. (Out of curiosity, which language? Feel free to not answer, or to answer off-list, as that's probably not constructive to the thread.) No problem. I'm using Scala. It has a sophisticated type system. The language is not perfect, but it seems to suit my needs fairly well. I cannot name a single modern programming language that does NOT have some kind of implicit boolification. The only such language I know of is REXX, which has a single data type for everything, but insists on the exact strings 1 and 0 for True and False, anything else is an error. Every other language has some definition of these things are true, these are false; for instance: Scala (and Java) don't do that. Nor does Ada. That's because Ada is designed for no-nonsense critical systems. It is the standard higher-order language for flight control systems, for example. It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. The looseness doesn't preclude critical applications. It's all a question of what you're testing. Does your code care that this be a list, and not something else? Then test! You have that option. What happens if it isn't a list, and something is done that bombs with an exception? Maybe that's not a problem. Critical applications can often be built in layers. For instance, a network server might listen for multiple socket connections, and for each connection, process multiple requests. You would want to catch exceptions at the two boundaries there; if a request handler crashes, the connection should not be dropped, and if a connection handler crashes, the server should keep running. With some basic defenses like that, your code need no longer concern itself with trivialities - if something goes wrong, there'll be an exception in the log. (BTW, this is one of the places where a bare or very wide except clause is appropriate. Log and move on.) Well, I don't really want to open the Pandora's box of static vs. dynamic typing. Yes, with enough testing, I'm sure you can get something good out of a dynamically typed language for small to medium-sized applications, but I have my doubts about larger applications. However, I don't claim to be an expert. Someone somewhere has probably developed a solid large application in Python. But I'll bet a dollar to a dime that it took more work than it would have taken in a good statically typed language. Yes, extensive testing can go a long way, but extensive testing combined with good static typing can go even further for the same level of effort. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 05/06/2013 07:11, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. I want to launch this rocket with an expensive satellite on top. I know it's safe as the code is written in ADA. Whoops :( -- Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green. Snooker commentator 'Whispering' Ted Lowe. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 6/5/2013 2:11 AM, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. I believe Shedskin, a Python *subset* compiler*, will reject that, because it compiles ints to C ints. Some code checkers might too. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 1:59:01 AM UTC-7, Mark Lawrence wrote: On 05/06/2013 07:11, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. I want to launch this rocket with an expensive satellite on top. I know it's safe as the code is written in ADA. Whoops :( So Python would have been a better choice? Yeah, right. If you know anything about that rocket mishap, you should know that Ada was not the source of the problem. Ada won't keep airplane wings from breaking either, by the way. It's not magic. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 2:15 AM, Russ P. russ.paie...@gmail.com wrote: On Wednesday, June 5, 2013 1:59:01 AM UTC-7, Mark Lawrence wrote: I want to launch this rocket with an expensive satellite on top. I know it's safe as the code is written in ADA. Whoops :( So Python would have been a better choice? Yeah, right. If you know anything about that rocket mishap, you should know that Ada was not the source of the problem. Ada won't keep airplane wings from breaking either, by the way. It's not magic. Frankly, I don't think the language much matters. It's all down to the skill of the programmers and testers. Ada wasn't the source of the problem unless Ada has a bug in it... which is going to be true of pretty much any language. Maybe Python would be a better choice, maybe not; but let me tell you this, if the choice of language means the difference between testable in three months and testable code in three years, I'm going for the former. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 9:59:07 AM UTC-7, Chris Angelico wrote: On Thu, Jun 6, 2013 at 2:15 AM, Russ P. wrote: On Wednesday, June 5, 2013 1:59:01 AM UTC-7, Mark Lawrence wrote: I want to launch this rocket with an expensive satellite on top. I know it's safe as the code is written in ADA. Whoops :( So Python would have been a better choice? Yeah, right. If you know anything about that rocket mishap, you should know that Ada was not the source of the problem. Ada won't keep airplane wings from breaking either, by the way. It's not magic. Frankly, I don't think the language much matters. It's all down to the skill of the programmers and testers. Ada wasn't the source of the problem unless Ada has a bug in it... which is going to be true of pretty much any language. Maybe Python would be a better choice, maybe not; but let me tell you this, if the choice of language means the difference between testable in three months and testable code in three years, I'm going for the former. ChrisA I'm not an Ada guy, but Ada advocates claim that it reduces development time by half in the long run compared to C and C++ due to reduced debugging time and simpler maintenance. Then again, I think Java people make a similar claim. As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. That requires the developer to keep much more of the design in his head, and that undesirable. Of course, you can always put the argument types in comments, but that won't be verified by the compiler. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 06/05/2013 12:11 AM, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. This comment shows me that you don't understand the difference between names, objects, and variables. May sound like a minor quibble, but there're actually major differences between binding names to objects (which is what python does) and variables (which is what languages like C have). It's very clear Rick does not have an understanding of this either. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 4:18:13 PM UTC-7, Michael Torrie wrote: On 06/05/2013 12:11 AM, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. This comment shows me that you don't understand the difference between names, objects, and variables. May sound like a minor quibble, but there're actually major differences between binding names to objects (which is what python does) and variables (which is what languages like C have). It's very clear Rick does not have an understanding of this either. My comment shows you nothing about what I understand about names, objects, and variables. You have chosen to question my understanding apparently because my point bothered you but you don't have a good reply. Then you link me with Rick for good measure. That's two ad hominems in three sentences. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 06/05/2013 05:52 PM, Russ P. wrote: My comment shows you nothing about what I understand about names, objects, and variables. Yes that probably is true. You have chosen to question my understanding apparently because my point bothered you but you don't have a good reply. Then you link me with Rick for good measure. That's two ad hominems in three sentences. Your statement didn't bother me. I just felt, perhaps erroneously, that such a comment needs clarification. We get into trouble in python when we get caught up in treating python names exactly like variables and blame it on the lack of static typing. In uni we looked at various means of dealing with the name covering/hiding issue including renaming or requiring that each binding be a unique name (meaning the second x = hello word statement would be a runtime error). Anyway, I got a bit distracted by your example of using the same name twice with different objects when the real issue that can cause pain is function call parameter expectation. My apologies for linking you to Rick. You're right that was an ad-hominem attack, though I didn't intend that! -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, 05 Jun 2013 09:15:01 -0700, Russ P. wrote: On Wednesday, June 5, 2013 1:59:01 AM UTC-7, Mark Lawrence wrote: On 05/06/2013 07:11, Russ P. wrote: But then, what would you expect of a language that allows you to write x = 1 x = Hello It's all loosey goosey -- which is fine for many applications but certainly not for critical ones. I want to launch this rocket with an expensive satellite on top. I know it's safe as the code is written in ADA. Whoops :( So Python would have been a better choice? Yeah, right. Putting issues of efficiency aside, yes, it probably would have. Had the programmers not been so sure that the compiler was protecting them from bugs, a misplaced hope if there ever was one, they might have written some tests and noticed that their simulated rocket launch ended up going boom instead of into orbit. I'm referring to the first test flight of the Ariane 5, which failed due to a software bug. There was no actual satellite on this flight. The failure Mark refers to was due to a leak in coolant pipes, which of course is a hardware problem and cannot be blamed on the software. http://en.wikipedia.org/wiki/Ariane_5#Notable_launches If you know anything about that rocket mishap, you should know that Ada was not the source of the problem. Ada won't keep airplane wings from breaking either, by the way. It's not magic. Again, referring to the infamous 64-bit float to 16-bit integer bug, Ada may not have been the *source* of the problem, but neither did it prevent it. What prevents bugs is the skill of the people writing the code, not the compiler. Compile-time static type checking is merely a tool, which has costs and benefits. It is ludicrous to think that any one single tool, or the lack of that tool, will make all the difference between working code and non-working code. Static type-checking is no better, or worse, for critical code than dynamic type-checking. One language chooses to deal with some errors at compile-time, others deal with them at run-time. Either way, the programmer has to deal with them in some way. A static type system forces you to deal with a limited subset of errors, type errors, in one way only: by removing any execution paths in the software which would assign data of type X to a variable of type Y. For reasons of machine efficiency, that is often a good was to deal with such errors. But a dynamic type system makes different trade-offs. And of course, type errors are such a vanishingly small subset of all the possible errors that might be made that, frankly, the difference in code quality between those with static typing and those without is essentially indistinguishable. There's no evidence that code written in static typed languages is less buggy than code written in dynamic languages. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 11:37 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: What prevents bugs is the skill of the people writing the code, not the compiler. +1 QOTW. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: I'm not an Ada guy, but Ada advocates claim that it reduces development time by half in the long run compared to C and C++ due to reduced debugging time and simpler maintenance. They may be right. Far too many people think that C and C++ are best of breed in static languages. They aren't. Then again, I think Java people make a similar claim. Java people would take credit for the sun coming up if they could :-) As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. Whereas people never get confused about the arguments in static typed languages? The only difference is whether the compiler tells you that you've passed the wrong type, or your unit test tells you that you've passed the wrong type. What, you don't have unit tests? Then how do you know that the code does the right thing when passed data of the right type? Adding an extra couple of unit tests is not that big a burden. Of course, if there was a way to automate that, why wouldn't you take advantage of it? Python currently has no standard way of doing such automated type tests, and probably won't ever get one. A static typed language gives you those tests for free, but in many languages at the cost that you probably end up spending more time fighting to satisfy the compiler than you save by not writing unit tests. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. Whereas people never get confused about the arguments in static typed languages? The only difference is whether the compiler tells you that you've passed the wrong type, or your unit test tells you that you've passed the wrong type. What, you don't have unit tests? Then how do you know that the code does the right thing when passed data of the right type? Adding an extra couple of unit tests is not that big a burden. The valid type(s) for an argument can be divided into two categories: Those the compiler can check for, and those the compiler can't check for. Some languages have more in the first category than others, but what compiler can prove that a string is an HTML-special-characters-escaped string? In a very few languages, the compiler can insist that an integer be between 7 and 30, but there'll always be some things you can't demonstrate with a function signature. That said, though, I do like being able to make at least *some* declaration there. It helps catch certain types of error. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wednesday, June 5, 2013 7:29:44 PM UTC-7, Chris Angelico wrote: On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: As for Python, my experience with it is that, as your application grows, you start getting confused about what the argument types are or are supposed to be. Whereas people never get confused about the arguments in static typed languages? The only difference is whether the compiler tells you that you've passed the wrong type, or your unit test tells you that you've passed the wrong type. What, you don't have unit tests? Then how do you know that the code does the right thing when passed data of the right type? Adding an extra couple of unit tests is not that big a burden. The valid type(s) for an argument can be divided into two categories: Those the compiler can check for, and those the compiler can't check for. Some languages have more in the first category than others, but what compiler can prove that a string is an HTML-special-characters-escaped string? In a very few languages, the compiler can insist that an integer be between 7 and 30, but there'll always be some things you can't demonstrate with a function signature. That said, though, I do like being able to make at least *some* declaration there. It helps catch certain types of error. I recall reading a few years ago that Guido was thinking about adding optional type annotations. I don't know if that went anywhere or not, but I thought it was a good idea. Eventually I got tired of waiting, and I realized that I just wanted a statically typed language, so I started using one. Steven's view on static vs. dynamic typing are interesting, but I think they are out of the mainstream, for whatever that's worth. Does that mean he is wrong? I don't know. But I do know that statically typed code just seems to me to fit together tighter and more solidly. Maybe it's a liberal/conservative thing. Do liberals tend to favor dynamic typing? -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Tue, Jun 4, 2013 at 11:37 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: The print function is the very definition of a syntactic sugar. For example: print(some sting) is much more readable than: sys.stdout.write(some string+\n) ... Again, the removal of a print function (or print statement) will not prevent users from calling the write method on sys.stdout or sys.stderr (or ANY stream object for that matter!) And you could abolish ALL of the builtins by requiring that you import ctypes and implement them all yourself. That is not the point of the term. If print() is mere syntactic sugar, then everything is syntactic sugar for Brainf* code. The point of syntactic sugar is that there is a trivially-equivalent underlying interpretation. For instance, in C, array subscripting is trivially equivalent to addition and dereferencing: a[i] - *(a+i) This is syntactic sugar. The Python print() function does much more than write(), so it is NOT syntactic sugar. Many times you'll get a result (or an input) that you expect to be a Boolean, but instead is a string. A good example of poor coding is dialog box return values. Take your standard yes/no/cancel dialog, i would expect it to return True|False|None respectively, HOWEVER, some *idiot* decided to return the strings 'yes'|'no'|'cancel'. Why True|False|None? Why should they represent Yes|No|Cancel? Especially, *why None*? What has None to do with Cancel? However, with Python's implicit conversion to Boolean, the same conditional will ALWAYS be True: because any string that is not the null string is True (as far as Python is concerned). This is an example of Python devs breaking TWO Zens at once: explicit is better than implicit errors should NEVER pass silently Right, because it's Python's fault that you can't use implicit boolean conversion to sanely test for something that has three possible outcomes. I think there's something in the nature of a boolean test that makes this awkward, but I can't quite see it... hmm, some kind of integer issue, I think... Obviously you don't appreciate the value of explicit enough. if VALUE: is not explicit enough, however if bool(VALUE) or at least: if VALUE == True is explicit enough. Why? The 'if' implies a boolean context. In C, it's common to compare integers for nonzeroness with a bare if; it's also common, though far from universal, to compare strings for nullness - effectively equivalent to is not None. You don't need to be any more explicit than that. Granted, the definitions of truthiness differ from language to language. In C, a NULL pointer is false and any actual pointer is true, so an empty string is true (to the extent that C even has the concept of strings, but leave that aside). In Pike, any array is true, but the absence of an array can be indicated with (effectively) a null, whereas Python deems that an empty list is false. Still, most languages do have some system of coercion-to-boolean. (Notable exception: REXX. An IF statement will accept *only* the two permitted boolean values, anything else is an error.) However, if i choose to be explicit and use: if len(VALUE) 0: then the code will fail when it should: at the comparison line. Because any object that does not provide a __len__ method would cause Python to raise NameError. I thought you were dead against wasting CPU cycles! Your code here has to calculate the actual length of the object, then compare it with zero; the simple boolean check merely has to announce the presence or absence of content. This is a HUGE difference in performance, and you should totally optimize this down for the sake of that. Don't bother measuring it, this will make more difference to your code than replacing bubble sort with bogosort! ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On 2 juin, 20:09, Rick Johnson rantingrickjohn...@gmail.com wrote: I never purposely inject ANY superfluous cycles in my code except in the case of testing or development. To me it's about professionalism. Let's consider a thought exercise shall we? The flexible string representation is the perfect example of this lack of professionalism. Wrong by design, a non understanding of the mathematical logic, of the coding of characters, of Unicode and of the usage of characters (everything is tight together). How is is possible to arrive to such a situation ? The answer if far beyond my understanding (although I have my opinion on the subject). jmf -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Jun 4, 5:23 pm, jmfauth wxjmfa...@gmail.com wrote: On 2 juin, 20:09, Rick Johnson rantingrickjohn...@gmail.com wrote: I never purposely inject ANY superfluous cycles in my code except in the case of testing or development. To me it's about professionalism. Let's consider a thought exercise shall we? The flexible string representation is the perfect example of this lack of professionalism. Wrong by design, a non understanding of the mathematical logic, of the coding of characters, of Unicode and of the usage of characters (everything is tight together). How is is possible to arrive to such a situation ? The answer if far beyond my understanding (although I have my opinion on the subject). jmf The Clash of the Titans Lé jmf chârgeth with mightƴ might And le Mond underneath trembleth Now RR mounts his sturdy steed And the windmill yonder turneth -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On 04/06/2013 14:29, rusi wrote: On Jun 4, 5:23 pm, jmfauth wxjmfa...@gmail.com wrote: On 2 juin, 20:09, Rick Johnson rantingrickjohn...@gmail.com wrote: I never purposely inject ANY superfluous cycles in my code except in the case of testing or development. To me it's about professionalism. Let's consider a thought exercise shall we? The flexible string representation is the perfect example of this lack of professionalism. Wrong by design, a non understanding of the mathematical logic, of the coding of characters, of Unicode and of the usage of characters (everything is tight together). How is is possible to arrive to such a situation ? The answer if far beyond my understanding (although I have my opinion on the subject). jmf The Clash of the Titans Lé jmf chârgeth with mightƴ might And le Mond underneath trembleth Now RR mounts his sturdy steed And the windmill yonder turneth +1 funniest poem of the week :) -- Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green. Snooker commentator 'Whispering' Ted Lowe. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Tuesday, June 4, 2013 12:39:59 AM UTC-5, Steven D'Aprano wrote: On Mon, 03 Jun 2013 18:37:24 -0700, Rick Johnson wrote: Consider a simple thought experiment. Suppose we start with a sequence of if statements that begin simple and get more complicated: if a == 1: ... if a == 1 and b 2*c: ... if a == 1 and b 2*c or d%4 == 1: ... if a == 1 and b 2*c or d%4 == 1 and not (d**3//7)%3 == 0: ... I don't believe that any of these tests are improved by adding an extraneous == True at the end: if (a == 1) == True: ... if (a == 1 and b 2*c) == True: ... if (a == 1 and b 2*c or d%4 == 1) == True: ... if (a == 1 and b 2*c or d%4 == 1 and not (d**3//7)%3 == 0) == True: ... And i agree! You are misunderstanding my very valid point. Post-fixing a == True when truth testing a *real* Boolean (psst: that's a True or False object) is superfluous, I'm referring to truth testing non-Boolean values. So with that in mind, the following is acceptably explicit enough for me: a = True if a: do_something() However, since Python allows implicit conversion to Boolean for ALL types, unless we know for sure, beyond any reasonable doubt, that the variable we are truth testing is pointing to a True or False object, we are taking too many chances and will eventually create subtle bugs. a = if a: do_something() When if write code that truth tests, i expect that the value i'm testing is a True or False object, not an empty list that *magically* converts to False when i place an if in front of it, or a list with more members that magically converts to True when i place an if in front of it. This implicit conversion seems like a good idea at first, and i was caught up in the hype myself for some time: Hey, i can save a few keystrokes, AWESOME!. However, i can tell you with certainty that this implicit conversion is folly. It is my firm belief that truth testing a value that is not a Boolean should raise an exception. If you want to convert a type to Boolean then pass it to the bool function: lst = [1,2,3] if bool(lst): do_something This would be explicit enough If you are unfamiliar with Python, then you have to learn what the semantics of if lst means. Just as you would have to learn what if len(lst) 0 means. Again, i understand the folly of implicit Boolean conversion just fine. I prefer to be explicit at the cost of a few keystrokes: if len(lst) 0: This line of code is problematic, for various reasons: - you're making assumptions about the object which are unnecessary; - which breaks duck-typing; - and risks doing too much work, or failing altogether. You're looking up the length of the lst object, but you don't really care about the length. Yes i do care about the length or i would not have asked. I'm asking Python to tell me if the iterable has members, amd if it does, i want to execute a block of code, if it does not, i want to do nothing. But i'm also informing the reader of my source code that the symbol i am truth testing is expected to be an iterable with a __len__ method. if lst does not give me the same answer (or imply the same meaning to a reader), it merely tells me that the implict conversion has resulted in a True value, but what if the lst symbol is pointing to a string? Then i will falsely believe i have a list with members when i actually have a string with length greater than zero. You only care about whether there is something there or not, whether lst is empty or not. It makes no difference whether lst contains one item or one hundred million items, and yet you're asking to count them all. Only to throw that count away immediately! I agree. Summing the list members just to guarantee that the iterable has members is foolish, however, python gives me no other choice IF i want to be explicit enough. In a properly designed language, the base iterable object would supply a hasLength or hasMembers method that would return a much faster check of: try: iterable[0] except IndexError: return False else: return True That check would guarantee the iterable contained at least one member without counting them all. Looking at the length of a built-in list is cheap, but why assume it is a built-in list? Perhaps it is a linked list where counting the items requires a slow O(N) traversal of the entire list. Or some kind of lazy sequence that has no way of counting the items remaining, but knows whether it is exhausted or not. Yes, but the problem is not my approach, rather the lack of proper language design (my apologizes to the anointed one. ;-) The Python way is to duck-type, and to let the lst object decide for itself whether it's empty or not: if lst: ... not to make assumptions about the specific type and performance of the object. Well Steven, in the real world sometimes you have no other choice. I don't have time to read and comprehend thousands of
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, Jun 5, 2013 at 1:44 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: But we are really ignoring the elephant in the room. Implict conversion to Boolean is just a drop in the bucket compared to the constant shell game we are subjected to when reading source code. We so naively believe that a symbol named lst is a list object or a symbol age is a integer, when we could be totally wrong! This is the source of many subtle bugs!!! You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I think one of them might even be used to make the most popular Python. Give it a try, you might like it! There's NO WAY that you could accidentally pass a list to a function that's expecting a float, NO WAY to unexpectedly call a method on the wrong type of object. It would suit you perfectly! ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 4 Jun 2013 17:04, Chris Angelico ros...@gmail.com wrote: On Wed, Jun 5, 2013 at 1:44 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: But we are really ignoring the elephant in the room. Implict conversion to Boolean is just a drop in the bucket compared to the constant shell game we are subjected to when reading source code. We so naively believe that a symbol named lst is a list object or a symbol age is a integer, when we could be totally wrong! This is the source of many subtle bugs!!! You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I think one of them might even be used to make the most popular Python. Give it a try, you might like it! There's NO WAY that you could accidentally pass a list to a function that's expecting a float, NO WAY to unexpectedly call a method on the wrong type of object. It would suit you perfectly! I agree. I have never had this kind of issues in a dynamic language. Except when passing stuff to Django's fields. And in JavaScript. It seems like the thing was made to create references to `undefined`. And make them easily convertible to numbers and strings so that our calculations mysteriously fail when we're missing a function argument somewhere. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 4, 10:44 am, Rick Johnson rantingrickjohn...@gmail.com wrote: What we need is a method by which we can validate a symbol and simultaneously do the vaidation in a manner that will cast light on the type that is expected. In order for this to work, you would need validators with unique type names if var.is_validList(): elif var.is_validString(): elif var.is_vaildTuple(): elif var.is_validInteger(): elif var.is_validFloat(): elif var.is_validDict(): etc... Actually, instead of forcing all types to have many specific methods, one builtin could solve the entire issue. The function would be similar to isinstance() taking two arguments object and type, however, it will not only guarantee type but also handle the conversion to Boolean: if is_valid(var, list): # if this block executes we know # the var is of type list and # var.length is greater than one. else: # if this block executes we know # that var is not of type list # or, var.length equals zero. The is_valid function would replace implicit Boolean conversion for all types in manner that is explicit enough whilst maintaining finger longevity. This is how you design a language for consistency and readability. Again. PUCKER UP WHO-VILLE! -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 4, 11:00 am, Chris Angelico ros...@gmail.com wrote: You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I don't like declaring types everywhere, i hate it. I prefer duck typed languages, HOWEVER, in order for duck typing to work consistently you must have checks and balances that the programmer can apply when he feels necessary. My is_valid built in will bridge the gap. We won't be forced to declare types, but we should ALWAYS add type checks to our truth tests unless we want to create subtle bugs. is_valid IS the answer! -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, Jun 5, 2013 at 2:19 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: On Jun 4, 11:00 am, Chris Angelico ros...@gmail.com wrote: You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I don't like declaring types everywhere, i hate it. I prefer duck typed languages, HOWEVER, in order for duck typing to work consistently you must have checks and balances that the programmer can apply when he feels necessary. My is_valid built in will bridge the gap. We won't be forced to declare types, but we should ALWAYS add type checks to our truth tests unless we want to create subtle bugs. is_valid IS the answer! Option 1: void C_function(int x) Option 2: def Python_function(x): assert isinstance(x,int) Is there a fundamental difference? You're basically proposing Option 2 while detesting Option 1. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 6/4/2013 12:19 PM, Rick Johnson wrote: On Jun 4, 11:00 am, Chris Angelico ros...@gmail.com wrote: You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I don't like declaring types everywhere, i hate it. I prefer duck typed languages, HOWEVER, in order for duck typing to work consistently you must have checks and balances that the programmer can apply when he feels necessary. My is_valid built in will bridge the gap. We won't be forced to declare types, but we should ALWAYS add type checks to our truth tests unless we want to create subtle bugs. is_valid IS the answer! You are mis-using the term duck typing. It doesn't mean just, no type declarations. It also means, the type of the value is irrelevant, all that matters is what it can do. Insisting that something be a list (or a dict, ...) is unnecessary and counter to the duck-typing philosophy. What's important is that you can iterate, or index it, or whatever it is you want to do with the list. The abstract base classes in the collections module were designed to help with determining these capabilities: http://docs.python.org/2/library/collections.html#collections-abstract-base-classes Of course, often, it's best just to do what you want to do rather than checking first. Also, I have no idea why [] isn't a valid list. Surely different applications will have different needs for what counts as valid once the type-check is passed. --Ned. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Tue, Jun 4, 2013 at 11:44 AM, Rick Johnson rantingrickjohn...@gmail.comwrote: This implicit conversion seems like a good idea at first, and i was caught up in the hype myself for some time: Hey, i can save a few keystrokes, AWESOME!. However, i can tell you with certainty that this implicit conversion is folly. It is my firm belief that truth testing a value that is not a Boolean should raise an exception. If you want to convert a type to Boolean then pass it to the bool function: lst = [1,2,3] if bool(lst): do_something This would be explicit enough i f lst: do_something is equivalent to if bool(lst): do_something why not just have your editor autobool so you can spend more time coding and less time stamping around? That way the person that finds booled code more readable can have what he wants and the people that find it less readable can have what they want. Win-win BTW, you should do pointless comparisons like if condition is True: do_something rather than if condition == True do_something -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Tue, Jun 4, 2013 at 9:44 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: It is my firm belief that truth testing a value that is not a Boolean should raise an exception. If you want to convert a type to Boolean then pass it to the bool function: lst = [1,2,3] if bool(lst): do_something This would be explicit enough That is *exactly* equivalent to the same test without the bool function, and it gives the reader zero additional information about what lst is, so it boggles me that you approve of this if bool(lst): monstrosity while decrying the equivalent and slightly more efficient if lst:. I think part of your complaint concerns the fact that the reader must understand the rules by which a truth value is implicitly obtained from lst in the statement if lst:. But the reader must know the *same* rules in order to understand the more explicit if bool(lst):, so there is no benefit to the latter in that regard either. Yes i do care about the length or i would not have asked. I'm asking Python to tell me if the iterable has members, amd if it does, i want to execute a block of code, if it does not, i want to do nothing. But i'm also informing the reader of my source code that the symbol i am truth testing is expected to be an iterable with a __len__ method. Caring that the object has a length is not the same as caring about what the object's length is. Steven's point stands, that your code inefficiently asks the object for some property that you don't (yet) care about. if lst does not give me the same answer (or imply the same meaning to a reader), it merely tells me that the implict conversion has resulted in a True value, but what if the lst symbol is pointing to a string? Then i will falsely believe i have a list with members when i actually have a string with length greater than zero. Your if len(lst) 0 fails to differentiate lists from strings in exactly the same way. I agree. Summing the list members just to guarantee that the iterable has members is foolish, however, python gives me no other choice IF i want to be explicit enough. In a properly designed language, the base iterable object would supply a hasLength or hasMembers method that would return a much faster check of: try: iterable[0] except IndexError: return False else: return True That check would guarantee the iterable contained at least one member without counting them all. You said earlier in your post that bool(lst) was explicit enough, and this is exactly what it does. When i am writing code i prefer to be explicit enough so that IF my assumptions about the exact type of an object are incorrect, the code will fail quickly enough that i can easily find and correct the problem. In a duck-typing language you should not be making assumptions about the exact type of an object in the first place. If I'm writing a function that receives a list-like argument, then at the *most specific* I will assume that the object passed in is a MutableSequence (but since I prefer to keep my functions functional where practical, more usually I will assume only that the object is an iterable or a generic sequence). If the caller wants to pass in a deque or some user-defined generic MutableSequence instead, then let them do so. I will also clearly document that assumption; if the caller can't be bothered to read the docs and passes in an object that breaks that assumption, then that's their own damn problem when it doesn't work. This is a programming language for consenting adults. But we are really ignoring the elephant in the room. Implict conversion to Boolean is just a drop in the bucket compared to the constant shell game we are subjected to when reading source code. We so naively believe that a symbol named lst is a list object or a symbol age is a integer, when we could be totally wrong! This is the source of many subtle bugs!!! I am more likely to believe that an object is a list based on the documentation than on the mere fact that it is named lst. The variable *does* have documentation, doesn't it? If when debugging I have reason to suspect that the documentation is incorrect or is being ignored, then I'll add an assertion to test it. There must be some method by which we can truth test an iterable object and verify it has members, but do so in a manner that is valid for all types AND exposes the expected type in the method name. hmm... This is nonsense. If it exposes the expected type in the name, then it can only be valid for that expected type. Adding a method like is_valid to every object can seem logical, however, this can fail just as miserably as Python's current implicit bool. And, more disastrously, an is_valid method is not going to raise an error (where it should) because it works for all types. Actually it sounds completely illogical to me. What would be an invalid object? What we need is a method by
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 4, 12:42 pm, Ian Kelly ian.g.ke...@gmail.com wrote: By this manner, we can roll three common tests into one method: * Boolean conversion * member truthiness for iterables * type checking How exactly does this is_valid method perform the first two? Are you suggesting that an empty sequence should not be considered valid? I'm suggesting that the rules for Python's current implicit conversion to Boolean simply be moved into a explicit function named isvalid, that also does a type check. Here is some Python code that might help you understand. py def isvalid(object_, type_): ... if isinstance(object_, type_) and object_: ... return True ... return False py isvalid([], list) False py isvalid([1], list) True py isvalid(0, int) False py isvalid(1, int) True py isvalid({}, dict) False py isvalid(, str) False py isvalid( , str) True Now, let's go back to my earlier example of where i was expecting a list but got a string instead. If i use Python's current implicit conversion to Boolean my code will do something i don't want it to do. py lst = py if lst: ... print(I'm a liar) ... else: ... print(I'm honest) I'm a liar But unlike this simple example (which failed quickly) in the real world, it may not fail for a long time. And when it does fail, you will be pulling your hair out tracking down the origin of the bug. If however i use my isvalid function, my conditional will not lie to me: py lst = py if isvalid(lst, list): ... print(I'm a liar) ... else: ... print(I'm honest) I'm honest Now. You're not always going to need to isvalid function. Sometimes you just need to test type, sometimes you just need convert to Boolean, and sometimes you can just fly by the seat of your pants. The point is, remove implicitly and inject explicitly. Furthermore: If the current implicit conversion to Boolean can be optimized by Python, then there is no reason why an explicit isvalid function cannot -- any talk to the contrary is just BS. If you still feel that this idea is garbage, then, keep on writing your sloppy code. My proposal is the best method to handle the problems that arise with duck typed languages in a manner that is not restrictive or laborious -- it's actually quite elegant. *school-bell-rings* -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 05/06/2013 00:21, Rick Johnson wrote: [snip] Would you be kind enough not to smoke too much wacky baccy before posting, thanks. -- Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green. Snooker commentator 'Whispering' Ted Lowe. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 5, 2:09 am, Rick Johnson rantingrickjohn...@gmail.com wrote: This is how you design a language for consistency and readability. Great! Now you can shut up and get back to work on RickPython4000. Come back and let us know all about it when it's done. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Tue, 04 Jun 2013 05:23:19 -0700, jmfauth wrote: How is is possible to arrive to such a situation ? The answer if far beyond my understanding Truer words have never been spoken. (although I have my opinion on the subject). http://en.wikipedia.org/wiki/Dunning–Kruger_effect -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On 06/04/2013 05:21 PM, Rick Johnson wrote: If you still feel that this idea is garbage, then, keep on writing your sloppy code. My proposal is the best method to handle the problems that arise with duck typed languages in a manner that is not restrictive or laborious -- it's actually quite elegant. Like most of your proposals, this does not have anything to do with the python syntax itself. You just demonstrated code that does what you want. So use it then. Adopt it in your own code, encourage others to use it. No changes to Python are needed. If this technique proves its value, then it will be adopted. If not, it will die. Start using it in one of your major open source projects. *school-bell-rings* It's one thing to patronize people as you try to do to D'Aprano (and yes I admit that most replies to your posts are often patronizing to you in return), but you do realize this infantile attempt to try to make yourself look smarter than others really reflects poorly on you? I for one feel badly for you on this count, or at least embarrassed. So just a suggestion... drop the school bell and teacher stuff (or at least share your qualifications with us). It's really tiring, though to be fair not quite as tiring as trying to help someone with an iron skull get a CGI script working. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Wed, 05 Jun 2013 02:27:26 +1000, Chris Angelico wrote: On Wed, Jun 5, 2013 at 2:19 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: On Jun 4, 11:00 am, Chris Angelico ros...@gmail.com wrote: You know, if you want a language with strict type declarations and extreme run-time efficiency, there are some around. I don't like declaring types everywhere, i hate it. I prefer duck typed languages, HOWEVER, in order for duck typing to work consistently you must have checks and balances that the programmer can apply when he feels necessary. My is_valid built in will bridge the gap. We won't be forced to declare types, but we should ALWAYS add type checks to our truth tests unless we want to create subtle bugs. is_valid IS the answer! Option 1: void C_function(int x) Option 2: def Python_function(x): assert isinstance(x,int) Is there a fundamental difference? You're basically proposing Option 2 while detesting Option 1. How many years has Rick been coming here, proclaiming loudly how much he loves Python's duck-typing? Ten years? And yet, he still has no clue what it actually means. If you're performing a type-check, IT ISN'T DUCK-TYPING. Duck typing means you don't care whether you have an int, so long as whatever object you get is usable where an int is usable. Now, there are many places in my own code where I decide that I wish to prohibit duck-typing. Here I insist on an actual int, not just any old number. There are, sometimes, good reasons for this. But every time I do this, I am *not* duck-typing, I am doing a runtime type check which is completely opposite in intent to duck-typing. (There's no short name for this -- it's not quite static typing, because it happens at runtime and isn't enforced by the language.) It's almost like Rick declares that he's a great supporter of the free market, and that everyone should be free to buy and trade in whatever property they wish, while insisting that nothing can be bought or sold without permission from the government first. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Bools and explicitness [was Re: PyWart: The problem with print]
On Jun 5, 3:28 pm, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: How many years has Rick been coming here, proclaiming loudly x [a]nd yet, he still has no clue what x actually means. It's not just duck typing. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python Heisenbugs? (was: Re: PyWart: The problem with print)
On Mon, Jun 3, 2013 at 12:34 AM, Dan Sommers d...@tombstonezero.net wrote: On Mon, 03 Jun 2013 13:37:27 +1000, Tim Delaney wrote: With the increase in use of higher-level languages, these days Heisenbugs most often appear with multithreaded code that doesn't properly protect critical sections, but as you say, with lower-level languages uninitialised memory is a common source of them. Aside from an I/O caching bug directly affected by calling print or somefile.write (where somefile is stdout), how else could I create a Heisenbug in pure Python? The garbage collector can do this, but I think in practice it's ridiculously rare, since __del__ is almost never useful due to its unreliability*. The problem is that the garbage collector can do whatever it wants. For example, in CPython it is called after so many cycles have been created. This allows code and user actions to inadvertently affect the garbage collector, and therefore, the invocation of __del__. If your __del__ does anything that accesses mutable global state also used elsewhere, it's conceivable that the order of someone else's access and __del__'s invocation depends on the GC. One order or the other might be the wrong one which causes a failure. As it happens, the bt command in pdb creates a cycle and might trigger the garbage collector, causing __del__ to run immediately, and potentially hiding the failure. This isn't really pure python in that Python doesn't even guarantee __del__ is ever called at all, let alone why. It's completely implementation-specific, and not a property of Python the language. -- Devin .. [*] Some people use it as an unreliable fallback; this turns their magical autosaving code into an attractive and yet horribly dangerous nuisance. Friends don't let friends use __del__. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 3:49 PM, Michael Torrie torr...@gmail.com wrote: On 06/02/2013 12:18 PM, Rick Johnson wrote: On Sunday, June 2, 2013 12:49:02 PM UTC-5, Dan Sommers wrote: On Mon, 03 Jun 2013 03:20:52 +1000, Chris Angelico wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson [...] Or use the logging module. It's easy to get going quickly (just call logging.basicConfig at startup time), and with a little care and feeding, you can control the output in more ways than can fit into the margin. Oh, yeah, I'm sure it introduces some overhead. So does everything else. I hate log files, at least during development or testing. I prefer to debug on the command line or using my IDE. Log files are for release time, not development. Except that it's not. Have you even looked at what the logging module is? It most certainly can log to stderr if you provide no logging handler to write to a file. Plus, writing to a file actually makes a lot of sense for development too. It's far easier to run the program the same way in dev and release, which often means daemonized. I like to have Upstart manage all my services, for instance. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, 03 Jun 2013 17:17:12 +1000, Chris Angelico wrote: On Mon, Jun 3, 2013 at 3:49 PM, Michael Torrie torr...@gmail.com wrote: On 06/02/2013 12:18 PM, Rick Johnson wrote: On Sunday, June 2, 2013 12:49:02 PM UTC-5, Dan Sommers wrote: On Mon, 03 Jun 2013 03:20:52 +1000, Chris Angelico wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson [...] Or use the logging module. It's easy to get going quickly (just call logging.basicConfig at startup time), and with a little care and feeding, you can control the output in more ways than can fit into the margin. Oh, yeah, I'm sure it introduces some overhead. So does everything else. I hate log files, at least during development or testing. I prefer to debug on the command line or using my IDE. Log files are for release time, not development. Except that it's not. Have you even looked at what the logging module is? It most certainly can log to stderr if you provide no logging handler to write to a file. Plus, writing to a file actually makes a lot of sense for development too. It's far easier to run the program the same way in dev and release, which often means daemonized. I like to have Upstart manage all my services, for instance. ChrisA further point the production logging code needs to be implemented and tested at development time anyway so why not make use of it instead of creating additional redundant code? -- It is a lesson which all history teaches wise men, to put trust in ideas, and not in circumstances. -- Emerson -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On 03/06/2013 04:10, Dan Sommers wrote: On Sun, 02 Jun 2013 20:16:21 -0400, Jason Swails wrote: ... If you don't believe me, you've never hit a bug that 'magically' disappears when you add a debugging print statement ;-). Ah, yes. The Heisenbug. ;-) We used to run into those back in the days of C and assembly language. They're much harder to see in the wild with Python. Strikes me it's a bit like problems when prototyping circuit boards. The card doesn't work, so you mount it on an extender card, problem goes away, remove extender card, problem reappears. Wash, rinse, repeat :) -- Steve is going for the pink ball - and for those of you who are watching in black and white, the pink is next to the green. Snooker commentator 'Whispering' Ted Lowe. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On 2013-06-03 05:20, Dan Sommers wrote: On Sun, 02 Jun 2013 23:23:42 -0400, Jason Swails wrote: ... (And yes, a good portion of our code is -still- in Fortran -- but at least it's F90+ :). I am a huge proponent of using the right tool for the job. There is nothing wrong with some well-placed FORTRAN, as long as the PSF No, no. It's the PSU that you have to worrNO CARRIER -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On 06/03/2013 04:49 AM, Mark Lawrence wrote: On 03/06/2013 04:10, Dan Sommers wrote: On Sun, 02 Jun 2013 20:16:21 -0400, Jason Swails wrote: ... If you don't believe me, you've never hit a bug that 'magically' disappears when you add a debugging print statement ;-). Ah, yes. The Heisenbug. ;-) We used to run into those back in the days of C and assembly language. They're much harder to see in the wild with Python. Strikes me it's a bit like problems when prototyping circuit boards. The card doesn't work, so you mount it on an extender card, problem goes away, remove extender card, problem reappears. Wash, rinse, repeat :) That's when you use a little kappy-zapper spray. -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Sun, Jun 2, 2013 at 6:16 PM, Jason Swails jason.swa...@gmail.com wrote: I'm actually with RR in terms of eliminating the overhead involved with 'dead' function calls, since there are instances when optimizing in Python is desirable. I actually recently adjusted one of my own scripts to eliminate branching and improve data layout to achieve a 1000-fold improvement in efficiency (~45 minutes to 0.42 s. for one example) --- all in pure Python. The first approach was unacceptable, the second is fine. For comparison, if I add a 'deactivated' debugprint call into the inner loop (executed 243K times in this particular test), then the time of the double-loop step that I optimized takes 0.73 seconds (nearly doubling the duration of the whole step). It seems to me that your problem here wasn't that the time needed for the deactivated debugprint was too great. Your problem was that a debugprint that executes 243K times in 0.73 seconds is going to generate far too much output to be useful, and it had no business being there in the first place. *Reasonably* placed debugprints are generally not going to be a significant time-sink for the application when disabled. The easiest way to eliminate these 'dead' calls is to simply comment-out the print call, but I would be quite upset if the interpreter tried to outsmart me and do it automagically as RR seems to be suggesting. Indeed, the print function is for general output, not specifically for debugging. If you have the global print deactivation that RR is suggesting, then what you have is no longer a print function, but a misnamed debug function. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 1:12 PM, Ian Kelly ian.g.ke...@gmail.com wrote: On Sun, Jun 2, 2013 at 6:16 PM, Jason Swails jason.swa...@gmail.com wrote: I'm actually with RR in terms of eliminating the overhead involved with 'dead' function calls, since there are instances when optimizing in Python is desirable. I actually recently adjusted one of my own scripts to eliminate branching and improve data layout to achieve a 1000-fold improvement in efficiency (~45 minutes to 0.42 s. for one example) --- all in pure Python. The first approach was unacceptable, the second is fine. For comparison, if I add a 'deactivated' debugprint call into the inner loop (executed 243K times in this particular test), then the time of the double-loop step that I optimized takes 0.73 seconds (nearly doubling the duration of the whole step). It seems to me that your problem here wasn't that the time needed for the deactivated debugprint was too great. Your problem was that a debugprint that executes 243K times in 0.73 seconds is going to generate far too much output to be useful, and it had no business being there in the first place. *Reasonably* placed debugprints are generally not going to be a significant time-sink for the application when disabled. Well in 'debug' mode I wouldn't use an example that executed the loop 200K times -- I'd find one that executed a manageable couple dozen, maybe. When 'disabled,' the print statement won't do anything except consume clock cycles and potentially displace useful cache (the latter being the more harmful, since most applications are bound by the memory bus). It's better to eliminate this dead call when you're not in 'debugging' mode. (When active, it certainly would've taken more than 0.73 seconds) Admittedly such loops should be tight enough that debugging statements inside the inner loop are generally unnecessary, but perhaps not always. But unlike RR, who suggests some elaborate interpreter-wide, ambiguous ignore-rule to squash out all of these functions, I'm simply suggesting that sometimes it's worth commenting-out debug print calls instead of 'just leaving them there because you won't notice the cost' :). The easiest way to eliminate these 'dead' calls is to simply comment-out the print call, but I would be quite upset if the interpreter tried to outsmart me and do it automagically as RR seems to be suggesting. Indeed, the print function is for general output, not specifically for debugging. If you have the global print deactivation that RR is suggesting, then what you have is no longer a print function, but a misnamed debug function. Exactly. I was just trying to make the point that it is -occasionally- worth spending the time to comment-out certain debug calls rather than leaving 'dead' function calls in certain places. All the best, Jason -- Jason M. Swails Quantum Theory Project, University of Florida Ph.D. Candidate 352-392-4032 -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 1:12 PM, Ian Kelly ian.g.ke...@gmail.com wrote: On Sun, Jun 2, 2013 at 6:16 PM, Jason Swails jason.swa...@gmail.com wrote: I'm actually with RR in terms of eliminating the overhead involved with 'dead' function calls, since there are instances when optimizing in Python is desirable. I actually recently adjusted one of my own scripts to eliminate branching and improve data layout to achieve a 1000-fold improvement in efficiency (~45 minutes to 0.42 s. for one example) --- all in pure Python. The first approach was unacceptable, the second is fine. For comparison, if I add a 'deactivated' debugprint call into the inner loop (executed 243K times in this particular test), then the time of the double-loop step that I optimized takes 0.73 seconds (nearly doubling the duration of the whole step). It seems to me that your problem here wasn't that the time needed for the deactivated debugprint was too great. Your problem was that a debugprint that executes 243K times in 0.73 seconds is going to generate far too much output to be useful, and it had no business being there in the first place. *Reasonably* placed debugprints are generally not going to be a significant time-sink for the application when disabled. Well in 'debug' mode I wouldn't use an example that executed the loop 200K times -- I'd find one that executed a manageable couple dozen, maybe. When 'disabled,' the print statement won't do anything except consume clock cycles and potentially displace useful cache (the latter being the more harmful, since most applications are bound by the memory bus). It's better to eliminate this dead call when you're not in 'debugging' mode. Admittedly such loops should be tight enough that debugging statements inside the inner loop are generally unnecessary, but perhaps not always. But unlike RR, who suggests some elaborate interpreter-wide, ambiguous ignore-rule to squash out all of these functions, I'm simply suggesting that sometimes it's worth commenting-out debug print calls instead of 'just leaving them there because you won't notice the cost' :). The easiest way to eliminate these 'dead' calls is to simply comment-out the print call, but I would be quite upset if the interpreter tried to outsmart me and do it automagically as RR seems to be suggesting. Indeed, the print function is for general output, not specifically for debugging. If you have the global print deactivation that RR is suggesting, then what you have is no longer a print function, but a misnamed debug function. Exactly. I was just trying to make the point that it is -occasionally- worth spending the time to comment-out certain debug calls rather than leaving 'dead' function calls in certain places. All the best, Jason -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
ack, sorry for the double-post. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, 03 Jun 2013 15:09:48 -0400, Jason Swails wrote: But unlike RR, who suggests some elaborate interpreter-wide, ambiguous ignore-rule to squash out all of these functions, I'm simply suggesting that sometimes it's worth commenting-out debug print calls instead of 'just leaving them there because you won't notice the cost' :). +1 Further to this idea, many command line apps have a verbose mode, where they print status messages as the app runs. Some of these include multiple levels, so you can tune just how many messages you get, commonly: - critical messages only - important or critical messages - warnings, important or critical messages - status, warnings, important or critical messages - all of the above, plus debugging messages - all of the above, plus even more debugging messages Since this verbosity level is selectable at runtime, the code itself must include many, many calls to some equivalent to print, enough calls to print to cover the most verbose case, even though most of the time most such calls just return without printing. This is a feature. And like all features, it has a cost. If (generic) your application does not benefit from verbose print statements scattered all throughout it, *don't put them in*. But if it will, then there is a certain amount of overhead to this feature. Deal with it, either by accepting the cost, or by writing more code that trades off complexity for efficiency. It's 2013, not 1975, and computers have more than 32K of RAM and the slowest CPU on the market is a million times faster than the ones that took us to the moon, and quite frankly I have no sympathy for the view that CPU cycles are so precious that we mustn't waste them. If that were the case, Python is the wrong language. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Tue, Jun 4, 2013 at 6:31 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: ... quite frankly I have no sympathy for the view that CPU cycles are so precious that we mustn't waste them. If that were the case, Python is the wrong language. CPU cycles *are* valuable still, though. The efficiency of your code determines how well it scales - but we have to be talking 100tps vs 1000tps here. There needs to be a huge difference for it to be at all significant. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Sunday, June 2, 2013 1:58:30 PM UTC-5, Steven D'Aprano wrote: On Sun, 02 Jun 2013 10:04:00 -0700, Rick Johnson wrote: Oh Steven, you've really outdone yourself this time with the theatrics. I hope you scored some cool points with your minions. Heck, you almost had me convinced until i slapped myself and realized your whole argument is just pure BS. For the sake of the lemmings, i must dissect your BS and expose it's methane emitting innards for all to smell. Many languages provide a function, method, or statement by which users can write easily to stdout, and Python is no exception with it's own print function. However, whilst writing to stdout via print is slightly less verbose than calling the write method of sys.stdout, we don't really gain much from this function except a few keystrokes... is this ALL print should be? A mere syntactical sugar? Perhaps you should read the docs before asking rhetorical questions, because the actual answer is, No, print is not mere syntactical sugar saving a few keystrokes. [...] And perhaps you should read a dictionary and obtain (at minimum) a primary school level education in English before making such foolish statements, because, OBVIOUSLY you don't know the definition of syntactical sugar... shall i educate you? # Wikipedia: syntactic sugar # # In computer science, syntactic sugar is syntax within a # # programming language that is designed to make things # # easier to read or to express. It makes the language # # sweeter for human use: things can be expressed more# # clearly, more concisely, or in an alternative style that # # some may prefer[...] # The print function is the very definition of a syntactic sugar. For example: print(some sting) is much more readable than: sys.stdout.write(some string+\n) or: sys.stderr.write(some string+\n) or: streamFoo.write(blah) But wait, there's more! # Wikipedia: syntactic sugar (continued) # # [...]Specifically, a construct in a language is called # # syntactic sugar if it can be removed from the language # # without any effect on what the language can do: # # functionality and expressive power will remain the same. # Again, the removal of a print function (or print statement) will not prevent users from calling the write method on sys.stdout or sys.stderr (or ANY stream object for that matter!) The only mistake i made was to specify stdout.write specifically instead of generally referring to the print function as a sugar for stream.write(). I've found that many subtle bugs are caused by not limiting the inputs to sane values (or types). And with Python's duct typing [...] and implicit casting to Boolean, you end up with all sorts of misleading things happening! Maybe you're testing for truth values and get a string instead; which screws everything up!!! Only if you're a lousy programmer who doesn't understand Python's truth model. I understand the Python truth model quite well, i just don't happen to like it. Implicit conversion to Boolean breaks the law of least astonishment. Many times you'll get a result (or an input) that you expect to be a Boolean, but instead is a string. A good example of poor coding is dialog box return values. Take your standard yes/no/cancel dialog, i would expect it to return True|False|None respectively, HOWEVER, some *idiot* decided to return the strings 'yes'|'no'|'cancel'. If you tried to bool test a string (In a properly designed language that does NOT support implicit Boolean conversion) you would get an error if you tried this: py string = py if string: ... do_something() ERROR: Cannot convert string to Boolean! However, with Python's implicit conversion to Boolean, the same conditional will ALWAYS be True: because any string that is not the null string is True (as far as Python is concerned). This is an example of Python devs breaking TWO Zens at once: explicit is better than implicit errors should NEVER pass silently And even though Python does not raise an error, it should! A wise programmer may think he's solved the problem by writing a function called debugprint that looks like this: def debugprint(*args): if DEBUG == True: print(*args) No no no, that's not how you do it. It should be: if DEBUG == True == True: Wait, no, I got that wrong. It should be: if DEBUG == True == True == True: Hang on, I've nearly got
Re: PyWart: The problem with print
Rick Johnson wrote: Take your standard yes/no/cancel dialog, i would expect it to return True|False|None respectively, you clearly mean True / False / FileNotFound. ( http://thedailywtf.com/Articles/What_Is_Truth_0x3f_.aspx ) -- ZeD -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Monday, June 3, 2013 10:16:13 PM UTC-5, Vito De Tullio wrote: Rick Johnson wrote: Take your standard yes/no/cancel dialog, i would expect it to return True|False|None respectively, you clearly mean True / False / FileNotFound. No, i clearly meant what i said :-). FileDialogs only return one of two values; either a valid path or a value representing failure. I suppose FileNotFound is a custom exception? That will work however i wonder if exception handling is overkill for this? try: path = filedialog.open(path) except FileNotFound: return do_something(path) As opposed to: path = filedialog.open(path) if path: do_something(path) Or, if Python was really cool! if filedialog.open(path) as path: do_something(path) However, i think True|False|None is the best return values for a yes|no|cancel choice. Consider: result = yesnocancel(save changes?) if result: # Try to save changes and close. if self.fileSave(): app.close() else: show_error() elif result is False: # Close without saving changes. app.close() else: # Canceled: Do nothing. return -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Tue, 04 Jun 2013 05:16:13 +0200, Vito De Tullio wrote: Rick Johnson wrote: Take your standard yes/no/cancel dialog, i would expect it to return True|False|None respectively, you clearly mean True / False / FileNotFound. ( http://thedailywtf.com/Articles/What_Is_Truth_0x3f_.aspx ) No no, he actually means return True return False raise an exception Or perhaps 0 1 2 Or perhaps: 'yes' 'no' 'cancel' like all right-thinking people expect *wink* Of course the one thing that a programmer should never, ever do, under pain of maybe having to learn something, is actually check the documentation of an unfamiliar library or function before making assumptions of what it will return. If you follow this advice, you too can enjoy the benefits of writing buggy code. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Bools and explicitness [was Re: PyWart: The problem with print]
On Mon, 03 Jun 2013 18:37:24 -0700, Rick Johnson wrote: On Sunday, June 2, 2013 1:58:30 PM UTC-5, Steven D'Aprano wrote: On Sun, 02 Jun 2013 10:04:00 -0700, Rick Johnson wrote: A wise programmer may think he's solved the problem by writing a function called debugprint that looks like this: def debugprint(*args): if DEBUG == True: print(*args) No no no, that's not how you do it. It should be: if DEBUG == True == True: Wait, no, I got that wrong. It should be: if DEBUG == True == True == True: Hang on, I've nearly got it! if DEBUG == True == True == True == True: Or, you could program like a professional, and say: if DEBUG: Obviously you don't appreciate the value of explicit enough. if VALUE: is not explicit enough, however Consider a simple thought experiment. Suppose we start with a sequence of if statements that begin simple and get more complicated: if a == 1: ... if a == 1 and b 2*c: ... if a == 1 and b 2*c or d%4 == 1: ... if a == 1 and b 2*c or d%4 == 1 and not (d**3//7)%3 == 0: ... I don't believe that any of these tests are improved by adding an extraneous == True at the end: if (a == 1) == True: ... if (a == 1 and b 2*c) == True: ... if (a == 1 and b 2*c or d%4 == 1) == True: ... if (a == 1 and b 2*c or d%4 == 1 and not (d**3//7)%3 == 0) == True: ... At some point your condition becomes so complicated that you may wish to save it as a separate variable, or perhaps you need to check the flag in a couple of places and so calculate it only once. Moving the flag out into a separate variable doesn't make == True any more useful or helpful. flag = a == 1 if flag == True: ... But even if it did, well, you've just entered the Twilight Zone, because of course flag == True is just a flag, so it too needs to be tested with == True: flag = (a == 1) == True if flag == True: ... but that too is just a flag so it needs more explicitness... and so on forever. This conclusion is of course nonsense. Adding == True to your boolean tests isn't helpful, so there's no need for even one, let alone an infinite series of == True. if flag is as explicit as it needs to be. There's no need to artificially inflate the explicitness as if being explicit was good in and of itself. We don't normally write code like this: n += int(1) just to be explicit about 1 being an int. That would be redundant and silly. In Python, 1 *is* an int. [...] if lst: I don't like that because it's too implict. What exactly about the list are we wanting to test? If you are unfamiliar with Python, then you have to learn what the semantics of if lst means. Just as you would have to learn what if len(lst) 0 means. I prefer to be explicit at the cost of a few keystrokes: if len(lst) 0: This line of code is problematic, for various reasons: - you're making assumptions about the object which are unnecessary; - which breaks duck-typing; - and risks doing too much work, or failing altogether. You're looking up the length of the lst object, but you don't really care about the length. You only care about whether there is something there or not, whether lst is empty or not. It makes no difference whether lst contains one item or one hundred million items, and yet you're asking to count them all. Only to throw that count away immediately! Looking at the length of a built-in list is cheap, but why assume it is a built-in list? Perhaps it is a linked list where counting the items requires a slow O(N) traversal of the entire list. Or some kind of lazy sequence that has no way of counting the items remaining, but knows whether it is exhausted or not. The Python way is to duck-type, and to let the lst object decide for itself whether it's empty or not: if lst: ... not to make assumptions about the specific type and performance of the object. Consider the following: What if the symbol `value` is expected to be a list, however, somehow it accidentally got reassigned to another type. If i choose to be implicit and use: if value, the code could silently work for a type i did not intend, therefore the program could go on for quite some time before failing suddenly on attribute error, or whatever. `if len(lst) 0` also works for types you don't intend. Any type that defines a __len__ method which returns an integer will do it. Tuples, sets and dicts are just the most obvious examples of things that support len() but do not necessarily support all the things you might wish to do to a list. However, if i choose to be explicit and use: if len(VALUE) 0: then the code will fail when it should: at the comparison line. Except of course when it doesn't. Because any object that does not provide a __len__ method would cause Python to raise NameError. TypeError. By being explicit enough i will inject readability and safety into my code base. Unnecessary verbosity and redundancy,
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: * Woefully inadequate because: Switching on or off the debug messages is only valid in the current module that the function was imported. What if you want to kill all debugprint messages EVERYWHERE? Do you really want to edit debug = BOOLEAN in every source file OR do something stupid like import debugprint and edit the DEBUG constant OR even dumber, edit the debugprint source code? GAWD NO! Easy fix to this one. Instead of copying and pasting debugprint into everything, have it in a module and import it everywhere. Then the debug flag will be common to them all. Oh, and you probably want to add **kwargs to debugprint, because the print function does a lot more than sys.stdout.write does: print(1,2,3,4,sep='#') 1#2#3#4 * But even if you are willing to cope with all the switch- on-and-off nonsense, are you willing to have you code slowed by numerous calls to a dead function containing a comparison that will always be false? Hmm. Could be costly. Hey, you know, Python has something for testing that. timeit.timeit('debugprint(asdf)','def debugprint(*args):\n\tif not DEBUG: return\n\tprint(*args)\nDEBUG=False',number=100) 0.5838018519113444 That's roughly half a second for a million calls to debugprint(). That's a 580ns cost per call. Rather than fiddle with the language, I'd rather just take this cost. Oh, and there's another way, too: If you make the DEBUG flag have effect only on startup, you could write your module thus: if DEBUG: debugprint=print else: def debugprint(*args,**kwargs): pass So you can eliminate part of the cost there, if it matters to you. If a half-microsecond cost is going to be significant to you, you probably should be looking at improving other areas, maybe using ctypes/cython, or possibly playing with the new preprocessor tricks that have been being discussed recently. There's really no need to change the language to solve one specific instance of this problem. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
I don't think you go far enough. Obviously we need way more flexibility. A simple on/off is okay for some things, but a finer granularity would be really helpful because some things are more important than others. And why stop at stdout/stderr? We need to add a consistent way to output these messages to files too in case we need to reference them again. The messages should have a consistent format as well. Why add the same information to each message when it would be much simpler to simply define a default format and insert the real meat of the message into it? It really seems like we should already have something like this. Hmm. -- CPython 3.3.2 | Windows NT 6.2.9200 / FreeBSD 9.1 -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 3:30 AM, Andrew Berg robotsondr...@gmail.com wrote: I don't think you go far enough. Obviously we need way more flexibility. A simple on/off is okay for some things, but a finer granularity would be really helpful because some things are more important than others. And why stop at stdout/stderr? We need to add a consistent way to output these messages to files too in case we need to reference them again. The messages should have a consistent format as well. Why add the same information to each message when it would be much simpler to simply define a default format and insert the real meat of the message into it? It really seems like we should already have something like this. Hmm. You have a really good point there. I'm sure I could think of a really good way to do all this, but I'm stuck... it's like there's a log jam in my head... (Okay, maybe I should go to bed now, my puns are getting worse. Considering how late it is, I'll probably sleep like a log.) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, 03 Jun 2013 03:20:52 +1000, Chris Angelico wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: * Woefully inadequate because: Switching on or off the debug messages is only valid in the current module that the function was imported. What if you want to kill all debugprint messages EVERYWHERE? Do you really want to edit debug = BOOLEAN in every source file OR do something stupid like import debugprint and edit the DEBUG constant OR even dumber, edit the debugprint source code? GAWD NO! Easy fix to this one. Instead of copying and pasting debugprint into everything, have it in a module and import it everywhere. Then the debug flag will be common to them all. Or use the logging module. It's easy to get going quickly (just call logging.basicConfig at startup time), and with a little care and feeding, you can control the output in more ways than can fit into the margin. Oh, yeah, I'm sure it introduces some overhead. So does everything else. * But even if you are willing to cope with all the switch- on-and-off nonsense, are you willing to have you code slowed by numerous calls to a dead function containing a comparison that will always be false? Hmm. Could be costly ... Yeah, all that time that I have left over and have to find something else to do instead of debugging my program. What a waste! ;-) Dan -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Jun 2, 12:20 pm, Chris Angelico ros...@gmail.com wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson * Woefully inadequate because: Switching on or off the debug messages is only valid in the current module that the function was imported. What if you want to kill all debugprint messages EVERYWHERE? Do you really want to edit debug = BOOLEAN in every source file OR do something stupid like import debugprint and edit the DEBUG constant OR even dumber, edit the debugprint source code? GAWD NO! Easy fix to this one. Instead of copying and pasting debugprint into everything, have it in a module and import it everywhere. Then the debug flag will be common to them all. Ignoring the fact that you have import everywhere, what if you want to stop ALL debug messages? If you import everywhere to get them, you then have to edit everywhere to stop them. Oh, and you probably want to add **kwargs to debugprint, because the print function does a lot more than sys.stdout.write does: The kwargs to print are not germane to the issue, however noobs may be watching so glad you pointed that one out. [...] py timeit.timeit('debugprint(asdf) [...] 0.5838018519113444 That's roughly half a second for a million calls to debugprint(). That's a 580ns cost per call. Rather than fiddle with the language, I'd rather just take this cost. I never purposely inject ANY superfluous cycles in my code except in the case of testing or development. To me it's about professionalism. Let's consider a thought exercise shall we? Imagine your an auto mechanic. You customer brings in his car and asks you to make some repairs. You make the repairs but you also adjust the air/fuel ratio to run rich (meaning the vehicle will get less MPG). Do you still pat yourself on the back and consider you've done a professional job? I would not! However, you're doing the same thing as the mechanic when your code executes superflouos calls and burns cycles for no other reason than pure laziness. CPU's are not immortal you know, they have a lifetime. Maybe you don't care about destroying someone's CPU, however, i do! I just wonder how many of your creations (aka: monstrosities!) are burning cycles this very minute! [...] So you can eliminate part of the cost there, if it matters to you. If a half-microsecond cost is going to be significant to you, you probably should be looking at improving other areas, maybe using ctypes/cython, or possibly playing with the new preprocessor tricks that have been being discussed recently. There's really no need to change the language to solve one specific instance of this problem. That's like suggesting to the poor fella who's MPG is suffering (because of your incompetent adjustments!) to buy fuel additives to compensate for the loss of MPG. Why should he incur costs because you are incompetent? -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Sunday, June 2, 2013 12:49:02 PM UTC-5, Dan Sommers wrote: On Mon, 03 Jun 2013 03:20:52 +1000, Chris Angelico wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson [...] Or use the logging module. It's easy to get going quickly (just call logging.basicConfig at startup time), and with a little care and feeding, you can control the output in more ways than can fit into the margin. Oh, yeah, I'm sure it introduces some overhead. So does everything else. I hate log files, at least during development or testing. I prefer to debug on the command line or using my IDE. Log files are for release time, not development. -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Sun, 02 Jun 2013 10:04:00 -0700, Rick Johnson wrote: Many languages provide a function, method, or statement by which users can write easily to stdout, and Python is no exception with it's own print function. However, whilst writing to stdout via print is slightly less verbose than calling the write method of sys.stdout, we don't really gain much from this function except a few keystrokes... is this ALL print should be? A mere syntactical sugar? Perhaps you should read the docs before asking rhetorical questions, because the actual answer is, No, print is not mere syntactical sugar saving a few keystrokes. Help on built-in function print in module builtins: print(...) print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) Prints the values to a stream, or to sys.stdout by default. Optional keyword arguments: file: a file-like object (stream); defaults to the current sys.stdout. sep: string inserted between values, default a space. end: string appended after the last value, default a newline. flush: whether to forcibly flush the stream. Still not powerful enough for you? Easily fixed: import builtins # The higher the verbosity, the more messages are printed. verbosity = 2 def print(*args, level=1, **kwargs): if level = verbosity: builtins.print(*args, **kwargs) print(debug message, level=4) # Only prints if verbosity = 4 print(info message, level=3) print(warning message, level=2) print(critical message, level=1) # Only prints if verbosity = 1 Trivial enough to embed in each module that needs it, in which case each module can have its own verbosity global variable. Or you can put it in a helper module, with a single, application-wide global variable, and use it like this: import verbose_print print = verbose_print.print verbose_print.verbosity = 3 print(some message, level=4) Of course, in practice you would set the verbosity according to a command line switch, or an environment variable, or a config file, and not hard code it in your source code. I've found that many subtle bugs are caused by not limiting the inputs to sane values (or types). And with Python's duct typing Nothing worse than having pythons roaming through your ducts, eating your ducks. and implicit casting to Boolean, you end up with all sorts of misleading things happening! Maybe you're testing for truth values and get a string instead; which screws everything up!!! Only if you're a lousy programmer who doesn't understand Python's truth model. A wise programmer may think he's solved the problem by writing a function called debugprint that looks like this: def debugprint(*args): if DEBUG == True: print(*args) No no no, that's not how you do it. It should be: if DEBUG == True == True: Wait, no, I got that wrong. It should be: if DEBUG == True == True == True: Hang on, I've nearly got it! if DEBUG == True == True == True == True: Or, you could program like a professional, and say: if DEBUG: By the way, why is DEBUG a constant? Doesn't that defeat the purpose? However that solution is at best woefully inadequate and at worse a cycle burner! Certainly you don't want to be burning cycles. Imagine the pollution from the burning rubber tyres! * Woefully inadequate because: Switching on or off the debug messages is only valid in the current module that the function was imported. What if you want to kill all debugprint messages EVERYWHERE? You start by learning how Python works, and not making woefully incorrect assumptions. Do you really want to edit debug = BOOLEAN in every source file Python does not work that way. OR do something stupid like import debugprint and edit the DEBUG constant Heaven forbid that people do something that actually works the way Python is designed to work. OR even dumber, edit the debugprint source code? GAWD NO! * But even if you are willing to cope with all the switch- on-and-off nonsense, are you willing to have you code slowed by numerous calls to a dead function containing a comparison that will always be false? And of course you have profiled your application, and determined that the bottleneck in performance is the calls to debugprint, because otherwise you are wasting your time and ours with premature optimization. Life is hard. Sometimes you have to choose between performance and debugging. This realization has brought me to the conclusion that Python (and other languages) need a scoped print function. What is a scoped print function anyway? Well what i am proposing is that Python include the following debug switches in the language: -- Switch: __GLOBALDEBUG__ -- Global switching allows a programmer to instruct the interpreter to IGNORE all print functions or to EVALUATE all
Re: PyWart: The problem with print
On Sun, 02 Jun 2013 11:09:12 -0700, Rick Johnson wrote: Maybe you don't care about destroying someone's CPU, however, i do! And yet here you are, destroying millions of people's CPUs by sending them email or usenet messages filled with garbage. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 4:09 AM, Rick Johnson rantingrickjohn...@gmail.com wrote: On Jun 2, 12:20 pm, Chris Angelico ros...@gmail.com wrote: On Mon, Jun 3, 2013 at 3:04 AM, Rick Johnson * Woefully inadequate because: Switching on or off the debug messages is only valid in the current module that the function was imported. What if you want to kill all debugprint messages EVERYWHERE? Do you really want to edit debug = BOOLEAN in every source file OR do something stupid like import debugprint and edit the DEBUG constant OR even dumber, edit the debugprint source code? GAWD NO! Easy fix to this one. Instead of copying and pasting debugprint into everything, have it in a module and import it everywhere. Then the debug flag will be common to them all. Ignoring the fact that you have import everywhere, what if you want to stop ALL debug messages? If you import everywhere to get them, you then have to edit everywhere to stop them. Example: ## debugprint.py DEBUG = True def debugprint(*a,**kw): if DEBUG: return print(*a,**kw) ## every other module from debugprint import debugprint debugprint(I got imported!) def foo(): debugprint(I got foo'd!) See how many places you need to edit to change the DEBUG flag? You can even do it at run time with this version of the code: ## toggle debugging import debugprint debugprint.DEBUG = not debugprint.DEBUG And, as several others have pointed out, this is kinda sorta what the logging module does, only it does it better. Same method; you import the same module everywhere. It is THE SAME module. That's roughly half a second for a million calls to debugprint(). That's a 580ns cost per call. Rather than fiddle with the language, I'd rather just take this cost. I never purposely inject ANY superfluous cycles in my code except in the case of testing or development. To me it's about professionalism. Why do you use Python? Clearly the only professional option is to use raw assembler. Or possibly you could justify C on the grounds of portability. Let's consider a thought exercise shall we? Imagine your an auto mechanic. You customer brings in his car and asks you to make some repairs. You make the repairs but you also adjust the air/fuel ratio to run rich (meaning the vehicle will get less MPG). Do you still pat yourself on the back and consider you've done a professional job? I would not! However, you're doing the same thing as the mechanic when your code executes superflouos calls and burns cycles for no other reason than pure laziness. CPU's are not immortal you know, they have a lifetime. Maybe you don't care about destroying someone's CPU, however, i do! Better analogy: When you build a car, you incorporate a whole bunch of gauges and indicators. They clutter things up, and they're extra weight to carry; wouldn't the car get more MPG (side point: can I have my car get more OGG instead? I like open formats) if you omit them? I just wonder how many of your creations (aka: monstrosities!) are burning cycles this very minute! Every one that's written in a high level language. So that's Yosemite, Minstrel Hall, Tisroc, KokoD, RapidSend/RapidRecv, and Vizier. And that's just the ones that I've personally created and that I *know* are currently running (and that I can think of off-hand). They're wasting CPU cycles dealing with stuff that I, the programmer, now don't have to. Now let's see. According to my server, right now, load average is 0.21 - of a single-core Intel processor that was mid-range back in 2009. And that's somewhat higher-than-normal load, caused by some sort of usage spike a few minutes ago (and is dropping); normally, load average is below 0.10. At what point would it be worth my effort to rewrite all that code to eliminate waste? Considering that I could build a new server for a few hundred (let's say $1000 to be generous, though the exact price will depend on where you are), or rent one in a top-quality data center for $40-$55/month and not have to pay for electricity or internet, any rewrite would need to take less than two days of my time to be worthwhile. Let 'em burn cycles; we can always get more. So you can eliminate part of the cost there, if it matters to you. If a half-microsecond cost is going to be significant to you, you probably should be looking at improving other areas, maybe using ctypes/cython, or possibly playing with the new preprocessor tricks that have been being discussed recently. There's really no need to change the language to solve one specific instance of this problem. That's like suggesting to the poor fella who's MPG is suffering (because of your incompetent adjustments!) to buy fuel additives to compensate for the loss of MPG. Why should he incur costs because you are incompetent? He's welcome to push a wheelbarrow if he doesn't want the overhead of a car. The car offers convenience, but at a cost. This is an eternal tradeoff.
Re: PyWart: The problem with print
On Mon, Jun 3, 2013 at 4:58 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: I've found that many subtle bugs are caused by not limiting the inputs to sane values (or types). And with Python's duct typing Nothing worse than having pythons roaming through your ducts, eating your ducks. Steven, you misunderstand. It's more about using your ducts to type code. Have you seen the Mythbusters episode where they're trying to enter a building surreptitiously? (Crimes and Mythdemeanors 1, I think, if you want to look it up.) At one point, we can CLEARLY hear one of the hosts, moving along a duct, *typing*. We can hear the click-click-click of giant keys. Hah. Knew I could trust Youtube. http://www.youtube.com/watch?v=5LovGVrrIuk ChrisA -- http://mail.python.org/mailman/listinfo/python-list