Re: Return value of an assignment statement?
On Fri, 22 Feb 2008 11:00:17 -0800, Aahz wrote: It's just too convenient to be able to write L += ['foo'] without rebinding L. nitpickBut ``+=`` does rebind./nitpick Doesn't matter in this case but we've had confused programmers asking questions here when `L` is a class attribute and it's rebound to the instance, or if they tried it on a list in a tuple. Extending a list that's a read only property doesn't work either. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Equivalent of system()?
This link may help: http://love-python.blogspot.com/2008/02/execute-linux-commands-in-python.html On Feb 23, 10:44 am, Max [EMAIL PROTECTED] wrote: Is there a Python equivalent of C++'s system()? TIA -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
in 335100 20080222 123210 Steven D'Aprano [EMAIL PROTECTED] wrote: On Fri, 22 Feb 2008 08:12:56 +, Marc 'BlackJack' Rintsch wrote: A variable in programming languages is composed of a name, a memory location, possibly a type and a value. In C-like languages, where you put values in named and typed boxes, the memory location and type are attached to the name. In Python both belong to the value. But Python objects don't have names, so by your own definition, they aren't variables. Names are associated with namespaces, not objects. A name must have one and only one object bound to it at any one time; objects on the other hand can be bound to one name, or no name, or a thousand names. The object itself has no way of knowing what names it is bound to, if any. Or, to put it another way... Python doesn't have variables. In that case neither does any other OO language. -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie in python
On Feb 21, 5:52 am, [EMAIL PROTECTED] wrote: Hi anyone I'm very interesed to learn python and really willing to do so,but unfortunately dont know where to start, or what programs need to install to start. Can someone help me to get in the right track, and get a good move? Thanks for all help pls reply on [EMAIL PROTECTED] or [EMAIL PROTECTED] I'd first want to know if you are just new to Python or are new to programming generally. Second, for what reason do you want to learn Python? What is it that you want to do with it? -- http://mail.python.org/mailman/listinfo/python-list
Re: Boa Constructor Mac crash when adding menubar
On Feb 21, 2:08 am, Jacob Davis [EMAIL PROTECTED] wrote: hi. Every time I go through the Boa Constructor tutorial and I get to the Add a Menu Bar section, Boa Constructor crashes after I select a wx.menubar and then left click either in the Data or design frames. I saw a post on the internet from the usenet about this very question, but was from 2005, and there was a reply that there would be a fix, but I can't figure out if this issue was supposed to be resolved. thanks for any help jake Could it be you have an old version of Boa? In any case, I'd post this under the Help forum at the Boa site: http://sourceforge.net/projects/boa-constructor/ -- http://mail.python.org/mailman/listinfo/python-list
Re: xml escapedness
On Fri, Feb 22, 2008 at 6:41 PM, Robin Becker [EMAIL PROTECTED] wrote: Tim van der Leeuw wrote: On Fri, Feb 22, 2008 at 5:17 PM, Robin Becker [EMAIL PROTECTED] wrote: [...] Well -- you escape them in the save() method only when they contain XML charachters like , ? How about that, wouldn't that work? --Tim .. That might work, but there are all the ampersands etc etc to consider as well. So an escaped string could contain , but so can a raw string. -- Robin Becker The way I see it, is that escaped XML is sure to contain ampersands, but 'real' XML is sure to contain brackets. If it doesn't contain any angle-brackets, then what's XML about it - it contains no tags? ;-) So I guess that looking for or will work as a heuristic, in 99.% of the cases - if not more ;-) Oh, and yes I agree with the other posters that it would be better to store it unescaped, and escape it where you need it. Cheers, --Tim -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a open souce IDE writen by C( C++) or partly writen by C( C++)?
On Feb 22, 11:06 pm, Jesper polluks(#at#)post.tele.dk wrote: Give PyScripter fromhttp://www.mmm-experts.com/a try It is for Windows, though it is written in Delphi and not in C/C++ /Jesper zaley [EMAIL PROTECTED] skrev i en meddelelsenews:[EMAIL PROTECTED] Of course, python scripts debugger On 2ÔÂ22ÈÕ, ÏÂÎç3ʱ22·Ö, zaley [EMAIL PROTECTED] wrote: My project need a simple scripts debugger . I hope I can find something instructive Stefan Behnel дµÀ£º zaley wrote: Is there a open souce IDE writen by C( C++) or partly writen by C( C+ +)? Tons of them. What do you want to do with it? Stefan- Hide quoted text - - Show quoted text - But PyScripter is not a open source project -- http://mail.python.org/mailman/listinfo/python-list
Re: Globals or objects?
Steven D'Aprano [EMAIL PROTECTED] wrote: On Fri, 22 Feb 2008 18:53:54 +, tinnews wrote: But you're not comparing what the OP posted. He was comparing a global with an object with a single variable inside it. Either would work with the y = spam(arg) example above. What do you mean by an object with a single variable inside it? I don't understand what that is supposed to mean, or why you think it is the same as a global. Do you mean a Singleton? If so, then the answer is simple: using a Singleton argument instead of a global is better, because with a global you are stuck to always using the global (at least until you can re-write the code), but with the Singleton argument, you may be enlightened and *not* use a Singleton. But if you stop using the Singleton the code no longer does the same as it would with a global does it? That's a *good* thing, not a problem. The whole idea is to get away from the bad behaviour of globals, not find some other way to implement it. That's *exactly* what I was saying in the bit you snipped! :-) However it doesn't answer the OP's questionas to why he was advised to replace a global with a class *without* changing the way it was used. -- Chris Green -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
Dennis Lee Bieber wrote: On Fri, 22 Feb 2008 11:23:27 -0800, Jeff Schwab [EMAIL PROTECTED] declaimed the following in comp.lang.python: I'm about through with this discussion, but FWIW, this is a real gotcha for me and many others. This is a case where Python does not do what many programmers expect, and it at least takes some getting used-to. As opposed to the twice monthly shocked newbie discovering that a mutable as a function default doesn't reset on the next invocation? In that aspect, it all comes down to the difference between mutables and immutables in Python. You know what's illuminating the discussion? Everybody thinks they understand this issue, but the explanations are contradictory. It seems like half the folks think this is an issue of mutability vs. immutability, and the other half believe that has nothing to do with it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Bruno Desthuilliers wrote: Jeff Schwab a écrit : Bruno Desthuilliers wrote: Carl Banks a écrit : On Feb 20, 8:58 am, Tim Chase [EMAIL PROTECTED] wrote: You Used Python to Write WHAT? http://www.cio.com/article/185350 Furthermore, the power and expressivity that Python offers means that it may require more skilled developers. [...down to the summary...] Python may not be an appropriate choice if you: [...] * Rely on teams of less-experienced programmers. These developers may benefit from the wider availability of training for languages like Java and are less likely to make mistakes with a compile-time, type-checked language. (snip) C++ is a compile-time, type-checked language, which means it is totally safer for newbies than Python. Yep, your big company is totally safe with newbie C++ programmers. Mouarf ! Brillant demonstration, thanks Carl !-) (and BTW, +1 QOTW) NB: This is not a troll. (Please, nobody try to be cute with a yes it is reply.) NB : standard disclaimer about all the following being MVHO. c.l.python seem to be about the most close-minded of any of the currently popular language-specific news groups. May I suggest you take a tour on c.l.lisp then ?-) It's just taken for granted that Perl and C++, two of my personal favorite things in this world, inherently favor ugly, buggy code. I wouldn't say so. It's a fact that C++ is a really complex language with quite a lot of room for BigMistakes(tm), and that there's something like a 'my-code-is-more-cryptic-than-yours' culture in Perl. You cannot seriously argue on this. I'm not going to argue, because I'm tired of arguing. But I think you're SeriouslyMistaken(tm). Now this has nothing to do with the respective merits of both languages (FWIW, Perl, as a 'Practical Extracting and Reporting Language', beats any other language I know pants down), and I'd be sorry if you were to confuse what is mostly on the friendly jokes side with mere bashing. You may not have noticed, but quite a lot of people here have a working experience with either C++ and/or Perl. Yes. These jokes don't strike me as friendly, though. They strike me as ignorant and hostile. As for my above comment, it doesn't imply anything else than the fact that C++ is way harder to learn than Python (or Ruby etc...), and that bugs in C++ code are likely to have way more nasty results. Both of which I disagree with. I don't see how the same brain can believe it's much harder to do good things, yet much easier to do bad things, in the same language. The joke is not against C++, but about people asserting than static type checking is safer than dynamic type checking without realizing that what is really important is*runtime type checking - something C++ doesn't provide. C++ does provide some run-time type-checking, whereas Python offers virtually no static type-checking. Clearly, C++ does not natively have a run-time environment as powerful as Python's, and that's one of the primary reasons to use Python. If you need a heavyweight runtime environment available from C++, you have to provide one. This is a direct consequence of early design decisions intended to make C++ competitive with C. I have yet to see a runtime-heavy C++ library I really like, whereas Python, Ruby, and Java all have fantastic sets of run-time facilities. NB : As a side note, and while being myself a bit passionated when it comes to languages and my job in general, I would not go as far as labelling any language or technology as one of my favorite things in this world. That's OK. :) I really do feel that way, though. Call me a dork. That is the farthest thing from the truth as I see it. You can (and plenty of people will) write terrible code in any language, including Python. Indeed. Bad coders write bad code, period. And I think we've all been bad coders one day, and that we're all still bad coders sometimes. Aha! Now we're getting somewhere! To use Python effectively, you have to know something about how it works, and the same is true of Perl and C++. And of any other language. Now a decent C++ or Perl programmer can be proficient in Python in a couple weeks and become a master within a year at worst. And it seems that non-professional, occasional programmers (hobbyists, gamers, scientists, and any other kind of power user) are able to get their job done in Python without much pain. They can get their jobs done with C++ without much pain, too, given even a little bit of decent guidance. It's true that you *can* shoot yourself in the foot with C++, but you kind of have to work at it. (One good way is to write C code, and think it's C++.) But a newbie who's learning from a decent source (avoid the C++ for Morons style books) is likely (I contend) to be writing semi-useful programs about as fast as with Python, and to be writing heavy-duty
Re: Looking for suggestions on improving numpy code
On Feb 22, 11:37 pm, David Lees [EMAIL PROTECTED] wrote: I want to read and process a single column. Then why won't a list suffice? -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
George Sakkis wrote: On Feb 22, 2:15 pm, Jeff Schwab [EMAIL PROTECTED] wrote: Nicola Musatti wrote: The real sad thing is that nobody is likely to convince Guido to turn CPython into C++Python ;-) How difficult would that be? Could it be done in stages? I would be willing to spend some time on that kind of project. Yeah right.. what we need is yet another implementation of Python. At least Jython/IronPython/Pypy (and Pyrex, Cython, Shedskin, etc.) had a better motivation than my language is better than yours. I am sure your time, skills and experience would be much appreciated in more useful projects. Neither C++ nor C is my language, nor yours. I love all my children the same. :) That said, your point is well taken. What I would like is not so much a new Python implementation, as a vehicle to help demonstrate a few things to other Python users. Recently, I've had a few replies in tones that imply I'm on the brink of entering several kill-files, mostly because I express disagreement with a few closely held beliefs of some other c.l.p posters. For example, the following are widely held opinions with which I disagree: (1) Python is a gotcha-free language. (2) C++ is basically the same language as C, but more complicated. (3) Garbage collection is at least as desirable a language feature as deterministic destruction. (4) Static typing is inferior to dynamic typing. One of the things that's supposed to be great about Python is the user community, and in many ways, that community is wonderful; for example, both new and experienced users can quickly get a variety of solutions to any given coding issue, just by asking for help. In other ways, though, the Python community is just blindingly ignorant, arrogant, and argumentative. I expect my use of Python to increase in the coming years, so I want the best possible relationship with other regular users, especially on Usenet. To do that, I think it would be helpful to have an informed discussion. Instead, I mostly just the same old justifications for baseless bigotry: I worked with crappy [Perl or C++] code for ten years, so when I tell you [Perl or C++] encourages crappy code, I know what I'm talking about. These beliefs are accepted by just about everybody. You don't *really* think all these bright people are wrong, do you? C++ is not newbie-friendly; if you need proof, just look at all these really low-level ways you can screw yourself. When I see this silliness again and again, it really breaks my heart, because the culture of the software development industry has a strong effect on the quality of my own life. I care about clean air, because I breath it; clean water, because I drink it; and I am starting to become really concerned about the clarity of mind of the Python community, because I hope to rely on it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a open souce IDE writen by C( C++) or partly writen by C( C++)?
On Feb 23, 5:02 pm, zaley [EMAIL PROTECTED] wrote: On Feb 22, 11:06 pm, Jesper polluks(#at#)post.tele.dk wrote: Give PyScripter fromhttp://www.mmm-experts.com/atry It is for Windows, though it is written in Delphi and not in C/C++ /Jesper zaley [EMAIL PROTECTED] skrev i en meddelelsenews:[EMAIL PROTECTED] Of course, python scripts debugger On 2ÔÂ22ÈÕ, ÏÂÎç3ʱ22·Ö, zaley [EMAIL PROTECTED] wrote: My project need a simple scripts debugger . I hope I can find something instructive Stefan Behnel дµÀ£º zaley wrote: Is there a open souce IDE writen by C( C++) or partly writen by C( C+ +)? Tons of them. What do you want to do with it? Stefan- Hide quoted text - - Show quoted text - But PyScripter is not a open source project- Hide quoted text - - Show quoted text - But PyScripter is not a open source project- Hide quoted text -- http://mail.python.org/mailman/listinfo/python-list
RE: Article of interest: Python pros/cons for the enterprise
On Behalf Of Jeff Schwab When I see this silliness again and again, it really breaks my heart If you allow your heart to be broken by others' opinions, you're setting yourself up for a lot of disappointment IMHO. I personally used C++ for about 90% of my code for 10 years. During that time, I was chugging the C++ Kool-Aid so hard I almost peed myself. I still think that C++ is a beautiful language, but I have also come to think that starting a program with C++ is a premature optimization. I think that very few Python programmers today started with Python. Most of them came to Python for a reason. Regards, Ryan Ginstrom -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Ryan Ginstrom wrote: On Behalf Of Jeff Schwab When I see this silliness again and again, it really breaks my heart If you allow your heart to be broken by others' opinions, you're setting yourself up for a lot of disappointment IMHO. It's not so much their opinions, as the fact that their opinions strongly influence their work. But you're probably right, anyway. I personally used C++ for about 90% of my code for 10 years. During that time, I was chugging the C++ Kool-Aid so hard I almost peed myself. I still think that C++ is a beautiful language, but I have also come to think that starting a program with C++ is a premature optimization. I'm not much of a Kool Aid drinker. :) I just tend to find, when I develop anything non-trivial in a language other than C++, that I wish I had used C++, because it would have allowed me to enforce design semantics more efficiently. Optimization has nothing to do with it; I'm a firm believer in profiling before you optimize. I think that very few Python programmers today started with Python. Most of them came to Python for a reason. For several reasons, even! -- http://mail.python.org/mailman/listinfo/python-list
Re: Globals or objects?
Steven D'Aprano wrote: On Fri, 22 Feb 2008 18:53:54 +, tinnews wrote: But you're not comparing what the OP posted. He was comparing a global with an object with a single variable inside it. Either would work with the y = spam(arg) example above. What do you mean by an object with a single variable inside it? I don't understand what that is supposed to mean, or why you think it is the same as a global. Do you mean a Singleton? If so, then the answer is simple: using a Singleton argument instead of a global is better, because with a global you are stuck to always using the global (at least until you can re-write the code), but with the Singleton argument, you may be enlightened and *not* use a Singleton. But if you stop using the Singleton the code no longer does the same as it would with a global does it? That's a *good* thing, not a problem. The whole idea is to get away from the bad behaviour of globals, not find some other way to implement it. I think that advocation of a global singleton is not really solving the problem. Not the problem I perceive, anyway. From your comments it's difficult to see whether we share the same perceptions, so let me elucidate. The issue I have with globals is primarily that use of a global introduces a tight coupling between a function and its environment, since any environment that uses the function has to provide the global. It's true that a global singleton is a half-way step to a solution of the problem because it portends the true solution, which also solves the problem of multiple counts. That solution, of course, is to have the function become a method of some counter object, which can then be used to count many things. In other words (untested, so ignore the many Holden types that this will inevitably incur): bad.py: counter = 0 def count(n): global counter counter += n justasbadifnotworse.py: class bunch: pass; counter = bunch() bunch.count = 0 def count(n): counter.count += n better.py: class Counter: def __init__(self): self.count = 0 counter1 = Counter() counter2 = Counter() def count(n, counter): counter.count += n best.py: class Counter: def __init__(self): self.count = 0 def count(self, n): self.count += n Now the names I have chosen are pejorative, but this is typically the development you see in someone's programming style as they slowly (or not slowly) start to understand the value of the object-oriented approach. Unfortunately this sometimes goes too far, and people end up writing monster objects, with dozens of methods and lots of instance variables used to communicate between them. With that style of programming the instance variables introduce the same tight coupling between the methods that globals do in a less object-oriented style, and the code becomes just as difficult to understand. Only now there can be multiple instances of the badly-written function! Sometimes this is inevitable, but good programming style is about trying to strike the right balance between contexts. It is truly possible to write good and bad programs in any language you like, and rules like globals are bad need to be taken in context just like any other rule. After all, some things *have* to be global for our programs to make any sense at all, unless you want to adopt a truly functional style that has never appealed to me. I like my programs to have state. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: n00b with urllib2: How to make it handle cookie automatically?
7stud wrote: On Feb 21, 11:50 pm, est [EMAIL PROTECTED] wrote: class SmartRequest(): You should always define a class like this: class SmartRequest(object): unless you know of a specific reason not to. It's much easier, though, just to put __metaclass__ = type at the start of any module where you want exlusively new-style objects. And I do agree that you should use exclusively new-style objects without a good reason for not doing, though thanks to Guido's hard work it mostly doesn't matter. $ cat test94.py __metaclass__ = type class Rhubarb: pass rhubarb = Rhubarb() print type(Rhubarb) print type(rhubarb) $ python test94.py type 'type' class '__main__.Rhubarb' regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
Paul Rubin wrote: Steven D'Aprano [EMAIL PROTECTED] writes: Personally, I think the confusion of augmented assignments is not worth the benefit of saving typing a couple of characters. I think Guido's first decision, to leave += etc out of the language, was the right decision. It quite helpful to be able to say foo['bar'+lookup(baz)][blob(a)+frob(b)] += 1 without having to split it into separate statements to avoid repeating the function calls and their possible side effects. And that was the reason for eventually including them. I remember being very surprised when I learned that rebinding was possible at the option of the implementing object, but of course rebinding is inevitable when you have immutable objects that implement augmented assignments. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: can't set attributes of built-in/extension type
Neal Becker wrote:
Steve Holden wrote:
Neal Becker wrote:
Steve Holden wrote:
Neal Becker wrote:
7stud wrote:
On Feb 21, 11:19 am, Neal Becker [EMAIL PROTECTED] wrote:
I'm working on a simple extension. Following the classic 'noddy'
example.
In [15]: cmplx_int32
Out[15]: type 'numpy.cmplx_int32'
Now I want to add an attribute to this type. More precisely, I want
a class attribute.
cmplx_int32.test = 0
---
TypeError Traceback (most recent call
last)
/home/nbecker/numpy/ipython console in module()
TypeError: can't set attributes of built-in/extension
type 'numpy.cmplx_int32'
What am I missing?
class Dog(object):
def __setattr__(self, attr, val):
print TypeError: can't set attributes of built-in/extension
print type 'Dog.cmplx_int32'
d = Dog()
d.test = 0
--output:--
TypeError: can't set attributes of built-in/extension
type 'Dog.cmplx_int32'
Not quite, I'm setting a class attribute, not an attribute on an
instance.
Quite. The problem is that extension types' attributes are determined by
the layout of the object's slots and forever fixed in the C code that
implements them: the slots can't be extended, so there's no way to add
attributes. This is an efficiency feature: it would be *extremely* slow
to look up the basic types' attributes using late-binding (it would also
change the nature of the language somewhat, making it more like Ruby or
Self).
So the reason you can't do what you want to is the same reason why you
can't add attribute to the built-in types (which are, of course, clearly
mentioned in the error message).
object.anyoldname = You lose!
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: can't set attributes of built-in/extension type 'object'
If you look in typeobject.c you'll find this error message occurs when
the object's type isn't a PyHeapTypeObject (in other words, if it's one
of the built-in or extension types).
Thanks, but I'm a bit confused. After reading in my Python in a
Nutshell, I found that if after calling PyReady on my type object, if I
use PyDict_SetItemString (my_type_obj.tp_dict,)
That seems to work fine (which isn't exactly what it said in the Nutshell
book, but close).
I wanted to add an attribute to my type.
Specifically, my type object is a static cmplx_int32_scalar_obj.
After calling PyType_Ready (cmplx_int32_scalar_obj), then I did
PyDict_SetItemString (cmplx_int32_scalar_obj.tp_dict, dtype, (PyObject*)d1);
Now my type has the property:
cmplx_int32.dtype
dtype('cmplx_int32')
Now, I do see that I still can't set it:
cmplx_int32.dtype = 2
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: can't set attributes of built-in/extension type 'numpy.cmplx_int32'
In this case, I don't need to.
But I still don't know why I can have a python class and set class or instance
attributes as I like, but this type acts differently. What would I need to
do if I did want to allow arbitrary attributes to be set/added to my type?
I believe it's because PyType_Ready(), among its many other duties,
calls mro_internal() on the type. It seems obvious that one would want
to optimize the MRO by not allowing modifications. Yet in C it is
possible, as you point out, to do so. Hmm ...
I'll let you know if I come to any conclusion - a query to python-dev
would probably get an answer, but surely someone on this list knows already?
[Left this as a draft for a while to mull it over].
After further consideration I have concluded (without further scrutiny
of the source) that it's because the method slots in C-implemented types
are pointers to C functions not to Python functions. Would this make sense?
regards
Steve
--
Steve Holden+1 571 484 6266 +1 800 494 3119
Holden Web LLC http://www.holdenweb.com/
--
http://mail.python.org/mailman/listinfo/python-list
Re: graphing/plotting with python and interface builder
Jacob Davis schrieb: Hi. I am developing for mac and using Xcode and Interface Builder 3.0. I can make a simple application, but I am having a hard time trying to figure out a good way to create a graph or plot for a class project. Does anybody have any tips on where to get started, or on how to do this? I have searched far for several days now, but I don't know if I am on the right track. Any help is much appreciated. I use http://developer.snowmintcs.com/frameworks/sm2dgraphview/index.html under 10.4. I don't see why it shouldn't work under 10.5. I assume you use pyobjc? I had to use the signature-decorator to make the SM2DGraphDataSource-category work - but I'm not sure if pyobjc 2.0 changes anything in that respect. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: ILeo (IPython-Leo bridge); a marriage made in heaven?
Here is something cool that will rock your world (ok, excuse the slight hyperbole): Many thanks for this posting, Ville. It is indeed very cool: - It shows how Leo can be used *now* as an IPython notebook. - It expands the notion of what is possible with Leo/IPython/Python scripts. Your ideas are destined to be of great importance to both the IPython and Leo communities. I shall continue this discussion at: http://groups.google.com/group/leo-editor/browse_thread/thread/3747a122f913cd7f Edward Edward K. Ream email: [EMAIL PROTECTED] Leo: http://webpages.charter.net/edreamleo/front.html -- http://mail.python.org/mailman/listinfo/python-list
Re: Simple - looking for a way to do an element exists check..
Paul Rubin wrote: if any(x[0]==element[0] for x in a): How come this list comprehension isn't in [] brackets? -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting stdout from other processes
Hi, Miki wrote: The current official module to use is subprocess (pipe = Popen([client], stdout=PIPE)) However if the client is sending data, reading from the pipe.stdout will block the server. If you *need* to wait, then you can use pipe.wait(), otherwise do as Diez suggested and have a thread read the client output and propagate it to the main loop (maybe using Queue.Queue) Thanks both of you for your explanations. In fact, it did the trick. -- Matthias -- http://mail.python.org/mailman/listinfo/python-list
Re: Odd behaviour of *.pth files and Apache
On Thu, 21 Feb 2008 13:55:25 -0500 D'Arcy J.M. Cain [EMAIL PROTECTED] wrote: I tried searching the archives for information on this but nothing seemed to be germane. I am running Python sripts as CGI under Apache and I have a .pth file in site-packages that includes directory that has another .pth in it. Sometimes it picks up the paths in the second .pth and sometimes it does not. It always seems to work if I am working in a location not in the ServerRoot but if I use the main site it does not pick up the directories in the included .pth. I have more information now. It seems that it recurses the .pth files it finds in PYTHONPATH but not for directories found in the .pth files in site-packages. Is this expected behaviour? The documentation suggests that it should pick up both. -- D'Arcy J.M. Cain [EMAIL PROTECTED] | Democracy is three wolves http://www.druid.net/darcy/| and a sheep voting on +1 416 425 1212 (DoD#0082)(eNTP) | what's for dinner. -- http://mail.python.org/mailman/listinfo/python-list
Re: Simple - looking for a way to do an element exists check..
Boris Ozegovic wrote: Paul Rubin wrote: if any(x[0]==element[0] for x in a): How come this list comprehension isn't in [] brackets? It isn't list comprehension, it is generator expression http://en.wikipedia.org/wiki/Python_syntax_and_semantics#Generator_expressions -- Tero -- http://mail.python.org/mailman/listinfo/python-list
Prophet Muhammad the last Messenger in the Bible
Prophet Muhammad the last Messenger in the Bible http://www.islamhouse.com/p/51913 -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
[EMAIL PROTECTED] wrote:
What you can't do (that I really miss) is have a tree of assign-and-test
expressions:
import re
pat = re.compile('some pattern')
if m = pat.match(some_string):
do_something(m)
else if m = pat.match(other_string):
do_other_thing(m)
else:
do_default_thing()
What you want is:
for astring, afunc in ((some_string, do_something), (other_string,
do_other_thing)):
m = pat.match(astring)
if m:
afunc(m)
break
else:
do_default_thing()
That looks like the first realistic alternative I've seen. I find the
flow a little hard to follow, but I think that's mostly just because I'm
not accustomed to the syntax.
Your approach fits in my head a little more comfortably if none of the
lines are longer than eighty columns, if the for-loop isn't given an
else-clause (which still looks to my untrained eye like it should match
the preceding if), and if the break-statement is replaced with a
return-statement:
actions = (
('some_string', do_something),
('other_string', do_other_thing))
def find_action(pattern):
for string, action in actions:
m = pattern.match(string)
if m:
return action
return do_default_thing
find_action(re.compile('some pattern'))()
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Re: Return value of an assignment statement?
Jeff Schwab wrote:
mrstephengross wrote:
Hi all. In C, an assignment statement returns the value assigned. For
instance:
int x
int y = (x = 3)
In the above example, (x=3) returns 3, which is assigned to y.
In python, as far as I can tell, assignment statements don't return
anything:
y = (x = 3)
The above example generates a SyntaxError.
Is this correct? I just want to make sure I've understood the
semantics.
Yes, but there is valid syntax for the common case you mentioned:
y = x = 3
What you can't do (that I really miss) is have a tree of assign-and-test
expressions:
import re
pat = re.compile('some pattern')
if m = pat.match(some_string):
do_something(m)
else if m = pat.match(other_string):
do_other_thing(m)
else:
do_default_thing()
This is apparently section 1.9 of the Python Cookbook:
http://www.oreilly.com/catalog/pythoncook2/toc.html
Martelli suggests something similar to the thigamabob technique I use
(he calls it DataHolder). It's really more like the xmatch posted by
Paul Rubin.
Martelli also says, though, that if you need this, you're not thinking
Pythonically. I don't know what the Pythonic alternative is. The
iterating-over-pairs approach suggested by Bruno is the only alternative
I've seen.
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integrating python with owl
Hello, I have developed an ontology using protege owl and I wonder if you can help me get any documentation on how to integrate it with python. Thank you very much, Noorhan. __ Sent from Yahoo! Mail. A Smarter Inbox. http://uk.docs.yahoo.com/nowyoucan.html-- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote:
Jeff Schwab [EMAIL PROTECTED] writes:
The most traditional, easiest way to open a file in C++ is to use an
fstream object, so the file is guaranteed to be closed when the
fstream goes out of scope.
Python has this too, except it's using a special type of scope
created by the with statement.
Yes, this seems to be the Python way: For each popular feature of some
other language, create a less flexible Python feature that achieves the
same effect in the most common cases (e.g. lambda to imitate function
literals, or recursive assignment to allow x = y = z).
CPython offers a similar feature, since
you can create a temporary object whose reference count will become
zero at the end of the statement where it is defined:
$ echo world hello
$ python
file('hello').read()
'world\n'
CPython does not guarantee that the reference count will become zero
at the end of the statement. It only happens to work that way in your
example, because the file.read operation doesn't make any new
references to the file object anywhere.
It doesn't happen to work that way in the example; it works that way
by design. I see what you're saying, though, and it is a good point.
Given a statements of the form:
some_class().method()
The method body could create an external reference to the instance of
some_class, such that the instance would not be reclaimed at the end of
the statement.
Other code might well do
something different, especially in a complex multi-statement scope.
Your scheme's
It's not my scheme. I got it from Martelli.
determinism relies on the programmer accurately keeping
track of reference counts in their head, which is precisely what
automatic resource management is supposed to avoid.
This is a special case of the reference count being 1, then immediately
dropping to zero. It is simple and convenient. The approach is, as you
rightly point out, not extensible to more complicated situations in
Python, because the reference counting ceases to be trivial.
The point is that once you tie object lifetimes to scope, rather than
unpredictable garbage collection, you can predict with perfect ease and
comfort exactly where the objects are created and destroyed. If you can
then request that arbitrary actions be taken automatically when those
events happen, you can pair up resource acquisitions and releases very
easily. Each resource has an owner object whose constructor acquires,
and whose destructor releases. The resources are released in the
reverse order, which is almost always exactly what you want.
Suppose you are using objects that have to be closed when you have
finished with them. You would associate this concept with a type:
class Closer:
def __init__(self, closable):
self.closable = closable)
def __del__(self):
self.closable.close()
The C++-style paradigm would then let you do this:
def my_func(a, b, c):
a_closer = Closer(a)
b_closer = Closer(b)
c_closer = Closer(c)
# ... arbitrary code ...
If an exception gets thrown, the objects get closed. If you return
normally, the objects get closed. This is what with is supposed to
replace, except that it only seems to cover the trivial case of a
single, all-in-one cleanup func. That's only a direct replacement for a
single constructor/destructor pair, unless you're willing to have an
additional, nested with-statement for each resource.
Now suppose there is an object type whose instances need to be
released rather than closed; i.e., they have a release() method, but
no close() method. No problem: You have the Closer class get its
action indirectly from a mapping of types to close-actions. Whenever
you have a type whose instances require some kind of cleanup action, you
add an entry to the mapping.
class Closer:
actions = TypeActionMap()
# ...
def __del__(self):
actions[type(self.closable)](self.closable)
The mapping is not quite as simple as a dict, because of inheritance.
This is what function overloads and C++ template specializations are
meant to achieve. Similar functionality could be implemented in Python
via pure Python mapping types, represented above by TypeActionMap.
If you want
reliable destruction it's better to set it up explicitly, using
with.
That's true of the current language. I don't have enough experience
with with yet to know whether it's a realistic solution to the issue.
IMO, they are at least preferable to Java-style finally-clauses, but
probably not a replacement for C++-style RAII.
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Re: Simple - looking for a way to do an element exists check..
TeroV wrote: It isn't list comprehension, it is generator expression http://en.wikipedia.org/wiki/Python_syntax_and_semantics#Generator_expressions Nice. :) -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
On 21 Feb, 23:33, [EMAIL PROTECTED]
[EMAIL PROTECTED] wrote:
What you can't do (that I really miss) is have a tree of assign-and-test
expressions:
import re
pat = re.compile('some pattern')
if m = pat.match(some_string):
do_something(m)
else if m = pat.match(other_string):
do_other_thing(m)
else:
do_default_thing()
What you want is:
for astring, afunc in ((some_string, do_something), (other_string,
do_other_thing)):
m = pat.match(astring)
if m:
afunc(m)
break
else:
do_default_thing()
The Bruno transform? :-)
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Tkinter: Missing the last piece of the puzzle
I have a simple editor built into my visual parser. It has a File menu with typical New, Open, Save, Save As ... options. I now know how to set the options [en/dis]abled and how to check the Text widget's modified flag. Now I want to [en/dis]able those options. Can I ask the text to notify me when the modified flag changes? Can I set the statuses when the user clicks File, before the options are displayed? Do I need to create a checker on an independent thread that looks at the flag every few millis? (Tkinter deserves more respect. I've got a good-looking application growing quickly.) -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
On Feb 23, 3:44 pm, Jeff Schwab [EMAIL PROTECTED] wrote:
actions = (
('some_string', do_something),
('other_string', do_other_thing))
def find_action(pattern):
for string, action in actions:
m = pattern.match(string)
if m:
return action
return do_default_thing
find_action(re.compile('some pattern'))()
You don't need to pass the pattern, just pass the match function:
def find_action(match, actions=actions, default_action=None):
for string, action in actions:
if match(string):
return action
return default_action
find_action(re.compile('some pattern').match)()
--
Arnaud
--
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Re: Simple - looking for a way to do an element exists check..
On Feb 22, 7:01 pm, Paul McGuire [EMAIL PROTECTED] wrote: On Feb 22, 12:54 pm, Paul Rubin http://[EMAIL PROTECTED] wrote: Paul Rubin http://[EMAIL PROTECTED] writes: if any(x==element[0] for x in a): a.append(element) Should say: if any(x[0]==element[0] for x in a): a.append(element) I think you have this backwards. Should be: if not any(x[0]==element[0] for x in a): a.append(element) IMO Jason's solution of testing containment in a generator is better (more readable). if element[0] not in (x[0] for x in a): a.append(element) -- Paul Hankin -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
Arnaud Delobelle wrote:
On Feb 23, 3:44 pm, Jeff Schwab [EMAIL PROTECTED] wrote:
actions = (
('some_string', do_something),
('other_string', do_other_thing))
def find_action(pattern):
for string, action in actions:
m = pattern.match(string)
if m:
return action
return do_default_thing
find_action(re.compile('some pattern'))()
You don't need to pass the pattern, just pass the match function:
def find_action(match, actions=actions, default_action=None):
for string, action in actions:
if match(string):
return action
return default_action
find_action(re.compile('some pattern').match)()
That's cool. :)
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Re: Handling locked db tables...
On 2008-02-20 17:19, breal wrote: On Feb 20, 8:05 am, M.-A. Lemburg [EMAIL PROTECTED] wrote: On 2008-02-20 16:24, breal wrote: I have a db table that holds a list of ports. There is a column in_use that is used as a flag for whether the port is currently in use. When choosing a port the table is read and the first available port with in_use = 0 is used, updated to in_use = 1, used, then updated to in_use = 0. I am using MySQLdb and want to make sure I am locking the table when doing reads, writes, updates since there will be several instances of my program looking for available ports simultaneously. When I run a lock table mytable read I can do all of my transactions. But, when another cursor then tries to do the read I get an error unless the first process has been completed... unlocking the tables. How is this handled generally? This is normal database locking behavior. If you do an update to a table from one process, the updated row is locked until the transaction is committed. If another process wants to access that row (even if only indirectly, e.g. a select that does a query which includes the data from the locked row), that process reports a database lock or times out until the lock is removed by the first process. The reason is simple: you don't want the second process to report wrong data, since there's still a chance the first process might roll back the transaction. Most modern database allow row-level locking. I'm not sure whether MySQL supports this. SQLite, for example, only support table locking. Marc-Andre, Thanks for the reply. I understand that this is normal locking behavior. What I am looking for is a standard method to either loop the query until the table is unlocked, or put the query into some sort of queue. Basically my queries work like this. Request comes in PART I: LOCK TABLE port_usage READ; SELECT * FROM port_usage WHERE in_use = 0; Get available port UPDATE port_usage SET in_use = 1 WHERE port = available_port; UNLOCK TABLES; send request to available port and do some stuff until finished with port PART II: LOCK TABLE port_usage READ UPDATE port_usage SET in_use = 0 WHERE port = available_port; UNLOCK TABLES; Several of these *may* be happening simultaneously so when a second request comes in, and the first one has the table locked, I want to have the PART I sql still work. Any suggestions here? Ok, so you want to use the table to manage locks on a resource. This is tricky, since the SELECT and UPDATE operations do not happen atomically. Also a READ lock won't help, what you need is a WRITE lock. Note that the UPDATE causes an implicit WRITE lock on the row you updated which persists until the end of the transaction. The way I usually approach this, is to mark the row for usage using an indicator that's unique to the process/thread requesting the resource. In a second query, I fetch the marked resource via the indicator. When freeing the resource, I update the row, again using the indicator and also clear the indicator from the row. All this is done on an auto-commit connection, so that no locking takes place. Works great. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Feb 23 2008) Python/Zope Consulting and Support ...http://www.egenix.com/ mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ mxODBC, mxDateTime, mxTextTools ...http://python.egenix.com/ Try mxODBC.Zope.DA for Windows,Linux,Solaris,MacOSX for free ! eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 -- http://mail.python.org/mailman/listinfo/python-list
Web tutorial temporarily moved
My programming tutorial web site has been dead this past week. This is just to say that I have copied the English version to a temporary mirror: http://uk.geocities.com/[EMAIL PROTECTED]/ Normal service will hopefully be resumed soon. Just in case anyone was wondering where it had gone! :-) Alan Gauld Author of the Learn to Proram web site http://www.freenetpages.co.uk/hp/alan.gauld -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
On Feb 23, 2:59 am, Jeff Schwab [EMAIL PROTECTED] wrote: Dennis Lee Bieber wrote: On Fri, 22 Feb 2008 11:23:27 -0800, Jeff Schwab [EMAIL PROTECTED] declaimed the following in comp.lang.python: I'm about through with this discussion, but FWIW, this is a real gotcha for me and many others. This is a case where Python does not do what many programmers expect, and it at least takes some getting used-to. As opposed to the twice monthly shocked newbie discovering that a mutable as a function default doesn't reset on the next invocation? In that aspect, it all comes down to the difference between mutables and immutables in Python. You know what's illuminating the discussion? Everybody thinks they understand this issue, but the explanations are contradictory. It seems like half the folks think this is an issue of mutability vs. immutability, and the other half believe that has nothing to do with it. You mean like this: :=) def invoke_some_fct(parent): y = parent.x try: y += [ 'world' ] except: y += ( 'world', ) print y, parent.x class abc: def __init__(self): self.x=[ 'hello' ] invoke_some_fct(self) print self.x self.x=( 'hello', ) invoke_some_fct(self) print self.x hw = abc() -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
On Feb 23, 6:40 am, Jeff Schwab [EMAIL PROTECTED] wrote: Recently, I've had a few replies in tones that imply I'm on the brink of entering several kill-files, mostly because I express disagreement with a few closely held beliefs of some other c.l.p posters. A bit of advice: Python and C++ have almost no common ground in terms of what the priorties of the language are. So, if you're a big proponent of the language features of C++, you really ought to expect lots of disagreement over just about anything you opine. P.S. I've had much sharper disagreements with some Pythonistas over aspects of Python. None of them are in my killfile. One of the things that's supposed to be great about Python is the user community, and in many ways, that community is wonderful; for example, both new and experienced users can quickly get a variety of solutions to any given coding issue, just by asking for help. They say that about every small language community. In other ways, though, the Python community is just blindingly ignorant, arrogant, and argumentative. You're not exactly riding the humble bus there yourself, chief. Saying things like (in so many words), I'm just here because C++ doesn't have good runtime libraries, doesn't come off too well. and I am starting to become really concerned about the clarity of mind of the Python community, because I hope to rely on it. I think your expectations for the Python community are unreasonable. My advice to you, if you want a good relationship with the Python community, would be to keep the comparisons with C++ out of it as much as possible. Understand that a lot--a lot--of people are going to say bad things about C++ and various features that C++ implements. If you try to defend C++ every time that happens, you won't last long here. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: The big shots
Dotan Cohen wrote: On 20/02/2008, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: It's a bad sign. If you aren't keeping your thoughts to yourself, and thrashing about the world for a peer, a social network, a support group, or a community, then you missed the day in grammar school when they were handing out smiles. But they're not handing them out anymore. You talk in analogies. I don't understand them. I do not know Spanish, and maybe if I knew both Spanish and your local customs, I would understand your analogies. But as a Hebrew-speaking middle easterner, I don't. I am a native Spanish speaker and I don't understand him either. It is not cultural. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Marc 'BlackJack' Rintsch wrote: [...] Or are used to think of OOP as a graph of objects that are communicating with each other. In the value type style you are talking to copies of objects all the time which I find a bit confusing because *I* have to keep track of which maybe not so identical twin brother of an object I'm talking at each point. But C++ gives you both; you use values for things that have equality but not identity and (smart) pointers for the opposite case. Also it seems odd to me to copy large collections around instead of passing references. Your `izip()` creates a quite small `map` -- what about big ones. With mutable objects!? True, and in a serious application I'd probably pass the map by reference into the function. Still, it's rather likely that these copies are optimized away by the compiler; this is what VC++ does, for instance. Cheers, Nicola Musatti -- Nicola.Musatti at gmail dot com Home: http://nicola.musatti.googlepages.com/home Blog: http://wthwdik.wordpress.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: graphing/plotting with python and interface builder
Thanks for the reply. I have wxPython installed and have used it. with wx I have just been using the wx.lib.plot module and the graphing is fine (although in other posts I note some focus issues). I have been looking at moving to using interface builder 3.0 and building Cocoa apps because for a bigger project it might be faster and better code. I only want to make plots that show data... but I need to refresh the plot at every step. with wx.lib.plot, i just draw it again (performance is not too big of an issue). No user interaction is needed. I will check out Chaco. Like I said, I know how to use wx.lib.plot, so if there is a way that I can use the graphs created there that would be great... although I suspect that wx.lib.plot requires a frame as a parent, which I would not want to use since .nib files (from interface builder) would handle the gui side with PyObjC (a language which I don't know). Thanks Jake On Feb 22, 2008, at 10:30 PM, Peter Wang wrote: On Feb 22, 10:08 pm, Jacob Davis [EMAIL PROTECTED] wrote: Hi. I am developing for mac and using Xcode and Interface Builder 3.0. I can make a simple application, but I am having a hard time trying to figure out a good way to create a graph orplotfor a class project. Does anybody have any tips on where to get started, or on how to do this? I have searched far for several days now, but I don't know if I am on the right track. Any help is much appreciated. Thanks, Jake Jake, are you using any python-specific GUI libraries like wxPython, Qt, or Tk? The Chaco plotting toolkit (http://code.enthought.com/ chaco) supports several different mechanisms for rendering on OS X; the default is to render via Quartz, but this requires wx or Qt. I am also currently working on a (somewhat experimental) pure OpenGL backend, which doesn't require wxPython or Qt, just an active OpenGL context. Do you want to generate a fairly static plot, or do you want the user to be able to interact with it in some way? -Peter -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote:
Nicola Musatti [EMAIL PROTECTED] writes:
a = [f(x) + g(y) for x,y in izip(m1, m2) if h(x,y).frob() == 7]
[...]
There you replace one line of code with 40+ lines to get around the
absence of GC. Sounds bug-prone among other things.
Come on, you didn't define f, g, izip, h or frob either. It's more like
5 to one. Furthermore your code is more compact due to the existence of
list comprehensions, not because of GC. Had you written a loop the
difference would be smaller.
int f(int n) { return n * 2; }
int g(int n) { return ( n * 2 ) + 1; }
That is not a reasonable translation, since you've assumed the output
of f and g are integers that don't need to be dynamically allocated.
Maybe in the Python example, f and g and x and y are all bignums or
matrices or something like that.
In my example I return a map by value just to show that it can be
generalized to more complex data types. This is not C: in C++ you can go
a long way without allocating dynamic memory explicitly. In my example
std::map and std::vector do it for me.
Cheers,
Nicola Musatti
--
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Home: http://nicola.musatti.googlepages.com/home
Blog: http://wthwdik.wordpress.com/
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Hyphenation module PyHyphen-0.3 released
I am pleased to share with you the great features of the latest version. Large parts of the sources were completely rewritten. Also, they are now reasonably documented. Just go to http://pypi.python.org/pypi/PyHyphen/0.3 I was tempted to classify it as Beta. Indeed I am not aware of any bugs, but I haven't spent very much time for testing, just ran some word lists... Any feedback is greatly appreciated. Especially I would be interested in experiences under Windows. I can only test it under Linux. If there were a good soul to send me a DLL for Windows ([EMAIL PROTECTED]) , this would be terrific. Bests Leo -- http://mail.python.org/mailman/listinfo/python-list
Re: ILeo (IPython-Leo bridge); a marriage made in heaven?
Edward K Ream wrote: Here is something cool that will rock your world (ok, excuse the slight hyperbole): Many thanks for this posting, Ville. It is indeed very cool: - It shows how Leo can be used *now* as an IPython notebook. - It expands the notion of what is possible with Leo/IPython/Python scripts. Your ideas are destined to be of great importance to both the IPython and Leo communities. I shall continue this discussion at: http://groups.google.com/group/leo-editor/browse_thread/thread/3747a122f913cd7f Edward Edward K. Ream email: [EMAIL PROTECTED] Leo: http://webpages.charter.net/edreamleo/front.html Are you part of Leo? This smells like a marketing scheme to me. -- http://mail.python.org/mailman/listinfo/python-list
@synchronized dect'r c.
To whoso has a serious interest in multi-threading: What advanced thread techniques does Python support? 1) @synchronized @synchronized def function( arg ): behavior() Synchronized prevents usage from more than one caller at once: look up the function in a hash, acquire its lock, and call. def synchronized( func ): def presynch( *ar, **kwar ): with _synchlock: lock= _synchhash.setdefault( func, allocate_lock() ) with lock: return func( *ar, **kwar ) return presynch 2) trylock: trylock.acquire() returns False if the thread that currently owns it is currently blocking on a lock that the calling thread currently owns. with trylock: instead throws an exception. Implementation pending. If a timeout is specified, returns one of three values: Success, Failure, and Deadlock. 3) upon_acquiring( lockA, lockB )( function, *ar, **kwar ) upon_acquiring spawns new thread upon acquiring locks A and B. Optional UponAcquirer( *locks ) instance can guarantee they are always acquired in the same order, similar to the strategy of acquiring locks in order of ID, but does not rely on the implementation detail of having them. Just acquire them in the order with which the instance was initialized. The similar construction: while 1: lockA.acq() lockB.acq() Is likewise efficient (non-polling), except in the corner case of small numbers of locks and large numbers of free-acquire pairs, such as in large numbers of lock clients, spec. threads. 4) @with_lockarg with_lockarg wraps an acquisition call, as in 2 or 3, and passes a lock group to the function as a first parameter: yes, even supersceding object instance parameters. def function( locks, self, *ar, **kwar ): behavior_in_lock() locks.release() more_behavior() function is called with the locks already held, so sadly though, with locks: idiom is not applicable. 5) groupjoin for j in range( len( strats ) ): for k in range( j+ 1, len( strats ) ): branch: i.matches[ j,k ]= Match( strats[j], strats[k] ) #Match instances may not be initialized until... joinallthese() This ideal may be implemented in current syntax as follows: thg= ThreadGroup() for j in range( len( strats ) ): for k in range( j+ 1, len( strats ) ): @thg.branch( freeze( i ), freeze( j ) ) def anonfunc( i, j ): i.matches[ j,k ]= Match( strats[j], strats[k] ) #Match instances may not be initialized until... thg.groupjoin() Footnotes: 2: trylock actually checks a graph for cyclicity, not merely if the individual callee is already waiting for the caller. 3: upon_acquiring as usual, a parameter can be passed to indicate to the framework to preserve calling order, rather than allowing with lockC to run prior to a series of threads which only use lockA and lockB. 4: x87 hardware supports memory block pairs and cache pairs, which set a reverse-bus bit upon truth of rudimentary comparisons, alleviating the instruction stack of checking them every time through a loop; merely jump to address when match completes. Fortunately, the blender doubles as a circuit-board printer after hours, so production can begin at once. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Carl Banks wrote: On Feb 23, 6:40 am, Jeff Schwab [EMAIL PROTECTED] wrote: Recently, I've had a few replies in tones that imply I'm on the brink of entering several kill-files, mostly because I express disagreement with a few closely held beliefs of some other c.l.p posters. A bit of advice: Python and C++ have almost no common ground in terms of what the priorties of the language are. Producing software of measurable quality. Increasing developer productivity. Providing in-language support for formal design and development processes. I think the languages approach the same high-level goals, just from very different angles. So, if you're a big proponent of the language features of C++, you really ought to expect lots of disagreement over just about anything you opine. P.S. I've had much sharper disagreements with some Pythonistas over aspects of Python. None of them are in my killfile. Good to know. :) One of the things that's supposed to be great about Python is the user community, and in many ways, that community is wonderful; for example, both new and experienced users can quickly get a variety of solutions to any given coding issue, just by asking for help. They say that about every small language community. I'm not sure Python qualifies as a small community anymore. Language-based communities that continue to support free thought and open conversation over time are much more rare. The worst case scenario is (apologies in advance) the Lisp-style consensus: This language is just the best tool for every job, period. In other ways, though, the Python community is just blindingly ignorant, arrogant, and argumentative. You're not exactly riding the humble bus there yourself, chief. Saying things like (in so many words), I'm just here because C++ doesn't have good runtime libraries, doesn't come off too well. That's not how I feel, and I never meant to imply anything like it. Things I like about Python: - No separate compilation step during development - Emphasis on design-for-test - Extensibility from other languages - Clean syntax - Portability - Mainstream use and support - Excellent documentation - Large standard library - Progress by design, rather than ad hoc improvements - Design decisions value useful over neat-o - Support for data-as-code (or code-as-data) and I am starting to become really concerned about the clarity of mind of the Python community, because I hope to rely on it. I think your expectations for the Python community are unreasonable. Maybe. My advice to you, if you want a good relationship with the Python community, would be to keep the comparisons with C++ out of it as much as possible. Understand that a lot--a lot--of people are going to say bad things about C++ and various features that C++ implements. If you try to defend C++ every time that happens, you won't last long here. Thanks. I do value my sanity, and would like to preserve what's left of it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Replacing 'if __name__ == __main__' with decorator (was: Double underscores -- ugly?)
@mainmethod def main(...) and like this: @mainmethod(parser=myparser) def main(...) then you cannot use that decorator for a function that expects or allows a function as its first argument? Because how and If it's called with only one non-keyword parameter, then the language might have done it; if not, guaranteed not. (More succintly, if it's not, the language didn't.) So, to get: @mainmethod def main(...) you'll have to check the parameter counts, and you can never invoke with just one callable parameter, pretty easy; bulky; your choice between: @mainmethod() def main(...) Note: 'Non-keyword' -and- callable! -- http://mail.python.org/mailman/listinfo/python-list
Re: graphing/plotting with python and interface builder
I found SM2DGraphView, but I guess that I am too much of a newbie with interface builder and pyobjc to figure out how to get SM2DGraphView to work. Are there any good tutorials (or better yet, examples) of how to get SM2DGraphView to work? I don't know pyobjc well at all. Thanks Jake On Feb 23, 2008, at 5:54 AM, Diez B. Roggisch wrote: Jacob Davis schrieb: Hi. I am developing for mac and using Xcode and Interface Builder 3.0. I can make a simple application, but I am having a hard time trying to figure out a good way to create a graph or plot for a class project. Does anybody have any tips on where to get started, or on how to do this? I have searched far for several days now, but I don't know if I am on the right track. Any help is much appreciated. I use http://developer.snowmintcs.com/frameworks/sm2dgraphview/index.html under 10.4. I don't see why it shouldn't work under 10.5. I assume you use pyobjc? I had to use the signature-decorator to make the SM2DGraphDataSource-category work - but I'm not sure if pyobjc 2.0 changes anything in that respect. Diez -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a open souce IDE writen by C( C++) or partly writen by C( C++)?
On Feb 23, 4:02 pm, zaley [EMAIL PROTECTED] wrote: On Feb 22, 11:06 pm, Jesper polluks(#at#)post.tele.dk wrote: Give PyScripter fromhttp://www.mmm-experts.com/atry It is for Windows, though it is written in Delphi and not in C/C++ /Jesper zaley [EMAIL PROTECTED] skrev i en meddelelsenews:[EMAIL PROTECTED] Of course, python scripts debugger On 2ÔÂ22ÈÕ, ÏÂÎç3ʱ22·Ö, zaley [EMAIL PROTECTED] wrote: My project need a simple scripts debugger . I hope I can find something instructive Stefan Behnel дµÀ£º zaley wrote: Is there a open souce IDE writen by C( C++) or partly writen by C( C+ +)? Tons of them. What do you want to do with it? Stefan- Hide quoted text - - Show quoted text - But PyScripter is not a open source project Am I correct to say that the reason why you wanted an open source C++ IDE is because you wanted the freedom to modify your own programming environment? -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
On Feb 23, 11:39 am, Nicola Musatti [EMAIL PROTECTED] wrote:
Paul Rubin wrote:
Nicola Musatti [EMAIL PROTECTED] writes:
a = [f(x) + g(y) for x,y in izip(m1, m2) if h(x,y).frob() == 7]
[...]
There you replace one line of code with 40+ lines to get around the
absence of GC. Sounds bug-prone among other things.
Come on, you didn't define f, g, izip, h or frob either. It's more like
5 to one. Furthermore your code is more compact due to the existence of
list comprehensions, not because of GC. Had you written a loop the
difference would be smaller.
So here's three versions, for comparison:
a = [f(x) + g(y) for x,y in izip(m1, m2) if h(x,y).frob() == 7]
a = []
for x, y in izip(m1, m2):
if h(x, y).frob() == 7:
a.append(f(x) + g(y))
std::vectorint a;
for (std::someiterableint,int::iterator i = izip(m1, m2); !
i.finished(); ++i) {
if (h(i-first, i-second).frob() == 7)
a.push_back(f(i-first) + g(i-second));
}
Although the the benefits of static typing can be argued, surely you
can see the clarity tradeoffs that you make for it?
Some notes:
* izip() takes two iterables as input and returns an iterator, using
only O(1) memory at any given time. Your original version got this
wrong.
* I fudged the !i.finished() as I couldn't find an appropriate
official version in time for this post
* The iterator can't sanely be copied, so it probably needs to use
refcounting internally. Oops, that's GC...
* Whoever decided to keep C's i++ syntax for iterators should be shot
* x and y aren't named. They could be extracted, but it's just enough
effort that it's probably not worth it in C++.
--
http://mail.python.org/mailman/listinfo/python-list
Re: @synchronized dect'r c.
Corrections. Typographical error in the implementation of #1. def synchronized( func ): def presynch( *ar, **kwar ): with _synchlock: lock= _synchhash.setdefault( func, allocate_lock() ) with lock: return func( *ar, **kwar ) return presynch On footnote #4, one might need a vector of jump addresses, one for each context in which the word might be modified. Yes, this involves a miniature many small design in actual hardware memory, and definitely opens some doors to faster processing. As such, it may not be the best first structural element in paralell off-loading, but it's a good one. And yes, it's specialty RAM, for which RAM may not even be the right place. If a few KB of it is enough, just bump it up next to the cache, which may make for shorter cycles on the jump-back later. You probably don't want to be setting the instruction pointer from a KB's worth of addresses, so there's probably an extra cycle involved in setting the jump register, halting the IP, and signalling a jump. Interrupts may be suited too. Does the OS need to provide an API before a compiler can make use of it? On #4, the signatures func( self, locks ) vs. func( locks, self ) is open: just if you sometimes want locks to be the second parameter, and other times the first, as for non-class-member functions, there will be two methods, or a parameter to signal the difference. -- http://mail.python.org/mailman/listinfo/python-list
Re: Globals or objects?
On Sat, 23 Feb 2008 08:16:44 -0500, Steve Holden wrote: Steven D'Aprano wrote: On Fri, 22 Feb 2008 18:53:54 +, tinnews wrote: But you're not comparing what the OP posted. He was comparing a global with an object with a single variable inside it. Either would work with the y = spam(arg) example above. What do you mean by an object with a single variable inside it? I don't understand what that is supposed to mean, or why you think it is the same as a global. Do you mean a Singleton? If so, then the answer is simple: using a Singleton argument instead of a global is better, because with a global you are stuck to always using the global (at least until you can re-write the code), but with the Singleton argument, you may be enlightened and *not* use a Singleton. But if you stop using the Singleton the code no longer does the same as it would with a global does it? That's a *good* thing, not a problem. The whole idea is to get away from the bad behaviour of globals, not find some other way to implement it. I think that advocation of a global singleton is not really solving the problem. Not the problem I perceive, anyway. From your comments it's difficult to see whether we share the same perceptions, so let me elucidate. Thanks for the details. I do agree with you. It wasn't me that suggested that the OP create a global singleton, or that using such a beast was a good plan. I hope that my response that [paraphrasing] a global singleton was good because it lets the developer STOP using a global singleton can be seen in context of tinnews badgering me again and again to explain why using a global singleton is better than an old-style global variable. That's not a position I would take. [...] After all, some things *have* to be global for our programs to make any sense at all, unless you want to adopt a truly functional style that has never appealed to me. I like my programs to have state. Some things are global, yes, but very few of them need to be global variables in the sense we're discussing. Actually, in the sense of the OP's example, I don't believe anything *needs* to be a global variable, unless it's a deliberate design choice (e.g. a global flag controlling some aspect of program behaviour, which I see as a legitimate if restrictive choice). -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a open souce IDE writen by C( C++) or partly writen by C( C++)?
Lie wrote: On Feb 23, 4:02 pm, zaley [EMAIL PROTECTED] wrote: On Feb 22, 11:06 pm, Jesper polluks(#at#)post.tele.dk wrote: Give PyScripter fromhttp://www.mmm-experts.com/atry It is for Windows, though it is written in Delphi and not in C/C++ /Jesper zaley [EMAIL PROTECTED] skrev i en meddelelsenews:[EMAIL PROTECTED] Of course, python scripts debugger On 2ÔÂ22ÈÕ, ÏÂÎç3ʱ22·Ö, zaley [EMAIL PROTECTED] wrote: My project need a simple scripts debugger . I hope I can find something instructive Stefan Behnel дµÀ£º zaley wrote: Is there a open souce IDE writen by C( C++) or partly writen by C( C+ +)? Tons of them. What do you want to do with it? Stefan- Hide quoted text - - Show quoted text - But PyScripter is not a open source project Am I correct to say that the reason why you wanted an open source C++ IDE is because you wanted the freedom to modify your own programming environment? From the About window in PyScripter : A freeware, open source Python scripter integrated development environment created with the ambition to bring to the Python community the quality and functionality available in commercial IDEs available for other languages. So I think we could say PyScripter IS an open source project. -- http://mail.python.org/mailman/listinfo/python-list
Re: ILeo (IPython-Leo bridge); a marriage made in heaven?
On Feb 23, 10:54 pm, Ricardo Aráoz [EMAIL PROTECTED] wrote: Are you part of Leo? This smells like a marketing scheme to me. Yes, Edward is part of Leo and I am part of IPython. In fact, most of my income comes from selling IPython T-shirts at the local flea market and I therefore have to resort to shady operations like this to pump up my fading income. Hey, it pays the bills! Seriously, though; this *is* cool stuff. I have an updated version of the document here: http://vvtools.googlecode.com/files/ILeo_doc.txt -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] wrote: The most traditional, easiest way to open a file in C++ is to use an fstream object, so the file is guaranteed to be closed when the fstream goes out of scope. Out of interest, what is the usual way to manage errors that the operating system reports when it closes the file? -M- -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: On Fri, 22 Feb 2008 11:00:17 -0800, Aahz wrote: It's just too convenient to be able to write L += ['foo'] without rebinding L. nitpickBut ``+=`` does rebind./nitpick Usually, but there's an exception for lists, which a specific implementation for += that calls append. Or do I misunderstand you? C:\tmppython Python 2.4.4 (#71, Oct 18 2006, 08:34:43) [MSC v.1310 32 bit (Intel)] on win32 Type help, copyright, credits or license for more information. L = [1,2,3] id(L) 10351000 L += [4] id(L) 10351000 -- Tim Roberts, [EMAIL PROTECTED] Providenza Boekelheide, Inc. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Matthew Woodcraft wrote: Jeff Schwab [EMAIL PROTECTED] wrote: The most traditional, easiest way to open a file in C++ is to use an fstream object, so the file is guaranteed to be closed when the fstream goes out of scope. Out of interest, what is the usual way to manage errors that the operating system reports when it closes the file? By default, the fstream object just sets its failbit, which you can check manually by calling my_stream.fail(). If you want anything particular to take place on failure to close a stream, you either have to call close manually, or you need a dedicated object whose destructor will deal with it. Alternatively, you can tell the fstream ahead of time that you want exceptions thrown if particular actions fail. There's a convention that destructors don't ever throw exceptions, though, so it would be unusual to request an exception when close() fails. -- http://mail.python.org/mailman/listinfo/python-list
Python camping in Argentina
Hi! This post is to tell you about a Python event we had the last weekend. It was a Python camping, in Los Cocos, Córdoba, Argentina. More than 20 Python developers, some experienced, some new ones, joined together in a center where we made a lot of activities during four whole days: - We had a mini python bug day, closing 4 or 5 issues, but more important, two new developers know how the full process is. - Worked heavily on a PyAr project, CDPedia, that aims to release a part of the wikipedia (spanish pages, for example, ;) ) to be queried off line, distributable in a CD. The project, when finished, will give you the way to construct these CDs or DVDs with the subselection of the wikipedia that you want, with installers for different operating systems, full text searches, and everything, :) - Made a framework for handling Scenes, Layers, sprites movements, and menues in pyglet, thinking in PyWeek. - Worked with behaviour trees and perceptrons, for AI modeling (yes, with Python). - Made a translation of Trac to spanish, aiming to include it in a Trac branch that will handle localizations. - Had a Python Argentina formal meeting. - Worked on a Rubick cube game in pyglet. And of course, we lunched and dinner all together, played games, climbed a mountain (carrying the Python Argentina flag to the top, see the photos), and have a lot, lot of fun. All the photos, here: http://www.flickr.com/photos/[EMAIL PROTECTED]/sets/72157603938876036/ Regards, -- .Facundo Blog: http://www.taniquetil.com.ar/plog/ PyAr: http://www.python.org/ar/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python camping in Argentina
Facundo Batista [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] Looks like a great event. |And of course, we lunched and dinner all together, played games, What is the hexagon board game? And, is the one woman I saw in the group photo a programmer? (I am trying to entice my daughter!) tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] wrote: Matthew Woodcraft wrote: Jeff Schwab [EMAIL PROTECTED] wrote: The most traditional, easiest way to open a file in C++ is to use an fstream object, so the file is guaranteed to be closed when the fstream goes out of scope. Out of interest, what is the usual way to manage errors that the operating system reports when it closes the file? By default, the fstream object just sets its failbit, which you can check manually by calling my_stream.fail(). If you want anything particular to take place on failure to close a stream, you either have to call close manually, or you need a dedicated object whose destructor will deal with it. Alternatively, you can tell the fstream ahead of time that you want exceptions thrown if particular actions fail. There's a convention that destructors don't ever throw exceptions, though, so it would be unusual to request an exception when close() fails. I see. Then, unless you don't care about data loss passing silently, this 'most traditional' way to open a file is unsuitable for files opened for writing. -M- -- http://mail.python.org/mailman/listinfo/python-list
looking for open source simulink clone in python
Does anyone know of something like this? I've searched to no avail. GNUradio companion is promising but tied to gnuradio. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes: some_class().method() The method body could create an external reference to the instance of some_class, such that the instance would not be reclaimed at the end of the statement. Yes. Therefore there is no way to predict if the object will be be freed, without intimate knowledge of the semantics of the class and method. It's not my scheme. I got it from Martelli. Well, he's a very wise and knowledgable Pythonista, so I hope he's using the with statement by now. This is a special case of the reference count being 1, then immediately dropping to zero. It is simple and convenient. The approach is, as you rightly point out, not extensible to more complicated situations in Python, because the reference counting ceases to be trivial. It's not trivial even in the simplest case, like the one you cited of opening a file. Maybe you've shadows the open function to keep a cache of file contents or something. The point is that once you tie object lifetimes to scope, rather than unpredictable garbage collection, you can predict with perfect ease and comfort exactly where the objects are created and destroyed. Sure, fine, Python does that with the with statement and C++ does it with class destructors on automatic variables. The old kludge of some_class().method() creates an instance of some_class but does NOT tie it to a scope, for the reasons we've discussed. That's true of the current language. I don't have enough experience with with yet to know whether it's a realistic solution to the issue. IMO, they are at least preferable to Java-style finally-clauses, but probably not a replacement for C++-style RAII. It is a more general version of what C++ does, as I understand it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Nicola Musatti [EMAIL PROTECTED] writes: a = [f(x) + g(y) for x,y in izip(m1, m2) if h(x,y).frob() == 7] [...] There you replace one line of code with 40+ lines to get around the absence of GC. Sounds bug-prone among other things. Come on, you didn't define f, g, izip, h or frob either. It's more like 5 to one. Furthermore your code is more compact due to the existence of list comprehensions, not because of GC. Had you written a loop the difference would be smaller. No I don't need a loop if I don't use the listcomp. I could say a = map(lambda x,y: f(x)+g(y), ifilter(lambda x,y: h(x,y).frob==7, izip(m1, m2))) the listcomp is basically syntax sugar for that. The issue here is that Python is simply more expressive than C++, which doesn't support creation of higher order functions like that. However, one of the consequences of programming in this style is you allocate a lot of temporary objects which best managed by GC. -- http://mail.python.org/mailman/listinfo/python-list
Re: @synchronized dect'r c.
On Feb 23, 2:03 pm, [EMAIL PROTECTED] wrote: 1) [EMAIL PROTECTED] @synchronized def function( arg ): behavior() Synchronized prevents usage from more than one caller at once: look up the function in a hash, acquire its lock, and call. def synchronized( func ): def presynch( *ar, **kwar ): with _synchlock: lock= _synchhash.setdefault( func, allocate_lock() ) with lock: return func( *ar, **kwar ) return presynch No need for a global _synchhash, just hang the function lock on the function itself: def synch(f): f._synchLock = Lock() def synchedFn(*args, **kwargs): with f._synchLock: f(*args, **kwargs) return synchedFn You might also look at the PythonDecoratorLibrary page of the Python wiki, there is a synchronization decorator there that allows the function caller to specify its own lock object (in case a single lock should be shared across multiple functions). -- Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: Return value of an assignment statement?
Tim Roberts [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] | Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote: | | On Fri, 22 Feb 2008 11:00:17 -0800, Aahz wrote: | | It's just too convenient to be able to write | | L += ['foo'] | | without rebinding L. | | nitpickBut ``+=`` does rebind./nitpick | | Usually, but there's an exception for lists, which a specific | implementation for += that calls append. Or do I misunderstand you? There is no exception at the compiler level, and indeed, cannot be, because in general, the compiler *does not know* the types of either target or augment. target += augment is compiled, in effect, as compute target and load target_object compute and load augment_object call target_object.__iadd__(augment_object) store return_object at target In the list case, the rebinding is to the *same* object! -- because list.__iadd(l1,l2)__ returns l1 extended with l2 rather than a new list l1+l2, as the specification allows. Augmented (inplace) assignment is still assignment (binding). | C:\tmppython | Python 2.4.4 (#71, Oct 18 2006, 08:34:43) [MSC v.1310 32 bit (Intel)] on | win32 | Type help, copyright, credits or license for more information. | L = [1,2,3] | id(L) | 10351000 | L += [4] | id(L) | 10351000 L has been rebound to the same object, hence same id. Unfortunately, such rebinding is only visible (that I can think of) when it fails: t=([],) t[0]+=[1] Traceback (most recent call last): File pyshell#8, line 1, in -toplevel- t[0]+=[1] TypeError: object does not support item assignment t ([1],) The list comprising t[0] is extended by its __iadd__ method. The exception arises due to the subsequent attempted rebinding to t[0] (see dis output below), which is, of course, not permissible. t[0].extend([2]) t ([1, 2],) Extension without attempted illegal rebinding raises no error. CPython specifics: from dis import dis def fi(i): i+=1; return i dis(fi) 1 0 LOAD_FAST0 (i) 3 LOAD_CONST 1 (1) 6 INPLACE_ADD 7 STORE_FAST 0 (i) 10 LOAD_FAST0 (i) 13 RETURN_VALUE def fl(l): l += [1]; return l dis(fl) 1 0 LOAD_FAST0 (l) 3 LOAD_CONST 1 (1) 6 BUILD_LIST 1 9 INPLACE_ADD 10 STORE_FAST 0 (l) 13 LOAD_FAST0 (l) 16 RETURN_VALUE Treating the VM stack as a Python list, INPLACE_ADD executes something like stack[-2] = stack[-2].__iadd__(stack[-1]) stack.pop() # leaving returned object on top of stack Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: bus error/segfault from PyArg_ParseTuple in initproc with incorrect arg number
Miles Lubin wrote: I am using PyArg_ParseTuple to parse the arguments (ignoring the keyword arguments) to my initproc for a type I define. It seems that something goes wrong inside PyArg_ParseTuple when it gets the wrong number of arguments (my format string is OO); if the function isn't given exactly two arguments, I get a bus error on OS X and a segfault on Linux. If two arguments are given, the code runs as expected. This does not occur when using PyArg_ParseTuple in a normal method. Am I not using PyArg_ParseTuple correctly? Here's the relevant code: PyObject *a, *b; if (!PyArg_ParseTuple(args, OO, a, b)) return -1; The segfault occurs on this line, not on any line after. I have seen bus errors on FreeBSD when python runs out of stack space. -- - Andrew I MacIntyre These thoughts are mine alone... E-mail: [EMAIL PROTECTED] (pref) | Snail: PO Box 370 [EMAIL PROTECTED] (alt) |Belconnen ACT 2616 Web:http://www.andymac.org/ |Australia -- http://mail.python.org/mailman/listinfo/python-list
Re: Hyphenation module PyHyphen-0.3 released
On Feb 23, 8:35 pm, Dr. leo [EMAIL PROTECTED] wrote: I am pleased to share with you the great features of the latest version. Large parts of the sources were completely rewritten. Also, they are now reasonably documented. Just go tohttp://pypi.python.org/pypi/PyHyphen/0.3 I was tempted to classify it as Beta. Indeed I am not aware of any bugs, but I haven't spent very much time for testing, just ran some word lists... Any feedback is greatly appreciated. Especially I would be interested in experiences under Windows. I can only test it under Linux. If there were a good soul to send me a DLL for Windows ([EMAIL PROTECTED]) , this would be terrific. Bests Leo Looks interesting, and I'd love to provide a .pyd file, however I'm running into some problems :-( I've got VS 2005 on this machine and setup-tools is complaining about my Python being built with VS 2003. (I know what the problem is with intermingling runtime libraries, yet I can't downgrade my VS version...) I got a message that I could try using mingw32, so a quick download and the build step seemed to finish without any problems: C:\work\PyHyphen-0.3python setup.py build -c mingw32 running build running build_py running build_ext running build_scripts creating build\scripts-2.5 copying example.py - build\scripts-2.5 (I ran build_ext first, which is why there's so little output.) I copied the dictionary into build\lib.win32-2.5\dict and was able to import the library without getting any errors and run the example from http://pypi.python.org/pypi/PyHyphen/0.3 (from the build directory). I'm stuck at trying to install the package though...: C:\work\PyHyphen-0.3python setup.py install running install running build running build_py running build_ext error: Python was built with Visual Studio 2003; extensions must be built with a compiler than can generate compatible binaries. Visual Studio 2003 was not found on this system. If you have Cygwin installed, you can try compiling with MingW32, by passing -c mingw32 to setup.py. C:\work\PyHyphen-0.3python setup.py install -c mingw32 usage: setup.py [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...] or: setup.py --help [cmd1 cmd2 ...] or: setup.py --help-commands or: setup.py cmd --help error: invalid command 'mingw32' I don't know if I'm just doing it wrong, or if I can't use extensions compiled with mingw32 with the standard distribution Python executable? -- bjorn -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] [snip discussion of 'with' statements] | Yes, this seems to be the Python way: For each popular feature of some | other language, create a less flexible Python feature that achieves the | same effect in the most common cases (e.g. lambda to imitate function | literals, or recursive assignment to allow x = y = z). This is a rather acute observation. Another example is generators versus full coroutines (or continuations). Guido is content to capture 80% of the practical use cases of a feature. He never intended Python to be a 100% replace-everything language. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Terry Reedy [EMAIL PROTECTED] writes: | Yes, this seems to be the Python way: For each popular feature of some | other language, create a less flexible Python feature that achieves the | same effect in the most common cases (e.g. lambda to imitate function | literals, or recursive assignment to allow x = y = z). This is a rather acute observation. Another example is generators versus full coroutines (or continuations). Guido is content to capture 80% of the practical use cases of a feature. He never intended Python to be a 100% replace-everything language. I don't understand the lambda example due to not being sure what Jeff means by function literals. But in other languages, lambda is the basic primitive, and def or equivalent is syntax sugar. -- http://mail.python.org/mailman/listinfo/python-list
Re: Simple - looking for a way to do an element exists check..
On Feb 23, 6:18 pm, Paul Hankin [EMAIL PROTECTED] wrote: On Feb 22, 7:01 pm, Paul McGuire [EMAIL PROTECTED] wrote: On Feb 22, 12:54 pm, Paul Rubin http://[EMAIL PROTECTED] wrote: Paul Rubin http://[EMAIL PROTECTED] writes: if any(x==element[0] for x in a): a.append(element) Should say: if any(x[0]==element[0] for x in a): a.append(element) I think you have this backwards. Should be: if not any(x[0]==element[0] for x in a): a.append(element) IMO Jason's solution of testing containment in a generator is better (more readable). if element[0] not in (x[0] for x in a): a.append(element) -- Paul Hankin It may be more readable (although that's debatable), but it always traverses the entire list. If the list is short I'd use either the traditional for/else or the newer if all(...): if all(x[0] != element[0] for x in a): a.append(element) which allows for short-circuit evaluation -- I generally try to stay away from negating any() and all() because the logic often gets convoluted. If the lists are long enough to care, either rewrite use a set-based solution if the items are hashable, or keep the elements sorted and rewrite to use the bisect module if the elements can be ordered. -- bjorn -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Terry Reedy [EMAIL PROTECTED] writes: Jeff Schwab [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] [snip discussion of 'with' statements] | Yes, this seems to be the Python way: For each popular feature of some | other language, create a less flexible Python feature that achieves the | same effect in the most common cases (e.g. lambda to imitate function | literals, or recursive assignment to allow x = y = z). This is a rather acute observation. Another example is generators versus full coroutines (or continuations). Another example that comes to mind is with statement versus a macro system that allowed one to define custom statements based on try...finally. contextlib.contextmanager implements an even more specific subset of this functionality. -- http://mail.python.org/mailman/listinfo/python-list
Re: can't set attributes of built-in/extension type
Steve Holden wrote:
Neal Becker wrote:
Steve Holden wrote:
Neal Becker wrote:
Steve Holden wrote:
Neal Becker wrote:
7stud wrote:
On Feb 21, 11:19 am, Neal Becker [EMAIL PROTECTED] wrote:
I'm working on a simple extension. Following the classic 'noddy'
example.
In [15]: cmplx_int32
Out[15]: type 'numpy.cmplx_int32'
Now I want to add an attribute to this type. More precisely, I want
a class attribute.
cmplx_int32.test = 0
---
TypeError Traceback (most recent call
last)
/home/nbecker/numpy/ipython console in module()
TypeError: can't set attributes of built-in/extension
type 'numpy.cmplx_int32'
What am I missing?
class Dog(object):
def __setattr__(self, attr, val):
print TypeError: can't set attributes of built-in/extension
print type 'Dog.cmplx_int32'
d = Dog()
d.test = 0
--output:--
TypeError: can't set attributes of built-in/extension
type 'Dog.cmplx_int32'
Not quite, I'm setting a class attribute, not an attribute on an
instance.
Quite. The problem is that extension types' attributes are determined by
the layout of the object's slots and forever fixed in the C code that
implements them: the slots can't be extended, so there's no way to add
attributes. This is an efficiency feature: it would be *extremely* slow
to look up the basic types' attributes using late-binding (it would also
change the nature of the language somewhat, making it more like Ruby or
Self).
So the reason you can't do what you want to is the same reason why you
can't add attribute to the built-in types (which are, of course, clearly
mentioned in the error message).
object.anyoldname = You lose!
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: can't set attributes of built-in/extension type 'object'
If you look in typeobject.c you'll find this error message occurs when
the object's type isn't a PyHeapTypeObject (in other words, if it's one
of the built-in or extension types).
Thanks, but I'm a bit confused. After reading in my Python in a
Nutshell, I found that if after calling PyReady on my type object, if I
use PyDict_SetItemString (my_type_obj.tp_dict,)
That seems to work fine (which isn't exactly what it said in the Nutshell
book, but close).
I wanted to add an attribute to my type.
Specifically, my type object is a static cmplx_int32_scalar_obj.
After calling PyType_Ready (cmplx_int32_scalar_obj), then I did
PyDict_SetItemString (cmplx_int32_scalar_obj.tp_dict, dtype,
(PyObject*)d1);
Now my type has the property:
cmplx_int32.dtype
dtype('cmplx_int32')
Now, I do see that I still can't set it:
cmplx_int32.dtype = 2
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: can't set attributes of built-in/extension type
'numpy.cmplx_int32'
In this case, I don't need to.
But I still don't know why I can have a python class and set class or
instance
attributes as I like, but this type acts differently. What would I need to
do if I did want to allow arbitrary attributes to be set/added to my type?
I believe it's because PyType_Ready(), among its many other duties,
calls mro_internal() on the type. It seems obvious that one would want
to optimize the MRO by not allowing modifications. Yet in C it is
possible, as you point out, to do so. Hmm ...
I'll let you know if I come to any conclusion - a query to python-dev
would probably get an answer, but surely someone on this list knows already?
[Left this as a draft for a while to mull it over].
After further consideration I have concluded (without further scrutiny
of the source) that it's because the method slots in C-implemented types
are pointers to C functions not to Python functions. Would this make sense?
Just to close this one off, Neal wrote to python-dev and got the
following reply from Guido himself.
On Sat, Feb 23, 2008 at 4:55 PM, Neal Becker [EMAIL PROTECTED] wrote:
There is some discussion on this subject, archived here:
http://permalink.gmane.org/gmane.comp.python.general/560661
I wonder if anyone could shed some light on this subject?
(Or, help me understand, what is the difference between a type that I create
using python C api and a python class?)
This is prohibited intentionally to prevent accidental fatal changes
to built-in types (fatal to parts of the code that you never though
of). Also, it is done to prevent the changes to affect different
interpreters residing in the address space, since built-in types
(unlike user-defined classes) are shared between all such
interpreters.
--
--Guido van Rossum (home page: http://www.python.org/~guido/)
regards
Steve
--
Steve Holden+1 571 484 6266 +1 800 494 3119
Holden Web LLC http://www.holdenweb.com/
--
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Re: Simple - looking for a way to do an element exists check..
thebjorn [EMAIL PROTECTED] writes: If the lists are long enough to care, either rewrite use a set-based solution if the items are hashable, or keep the elements sorted and rewrite to use the bisect module if the elements can be ordered. Well, you want a tree data structure to have fast insertions to remember what items have already been seen. There's been a bunch of proposals for an ordered dict type that works like this. Some day... -- http://mail.python.org/mailman/listinfo/python-list
Re: @synchronized dect'r c.
On Feb 23, 6:19 pm, Paul McGuire [EMAIL PROTECTED] wrote: On Feb 23, 2:03 pm, [EMAIL PROTECTED] wrote: 1) [EMAIL PROTECTED] @synchronized def function( arg ): behavior() Synchronized prevents usage from more than one caller at once: look up the function in a hash, acquire its lock, and call. def synchronized( func ): def presynch( *ar, **kwar ): with _synchlock: lock= _synchhash.setdefault( func, allocate_lock() ) with lock: return func( *ar, **kwar ) return presynch No need for a global _synchhash, just hang the function lock on the function itself: def synch(f): f._synchLock = Lock() def synchedFn(*args, **kwargs): with f._synchLock: f(*args, **kwargs) return synchedFn You might also look at the PythonDecoratorLibrary page of the Python wiki, there is a synchronization decorator there that allows the function caller to specify its own lock object (in case a single lock should be shared across multiple functions). -- Paul- Hide quoted text - - Show quoted text - Why not just: def synched( f ): l= Lock() def presynched( *a, **kwa ): with l: return f( *a, **kwa ) It's not like the lock is ever used anywhere else. Besides, if it is, isn't the correct spelling: class Asynched: def __init__( self, func ): self.func, self.lock= func, Lock() def __call__( self, *a, **kwa ): return self.func( *a, **kwa ) and def synched( func ): return Asynched( func ) or even synched= Asynched ? -- http://mail.python.org/mailman/listinfo/python-list
Re: Simple - looking for a way to do an element exists check..
On Feb 24, 2:24 am, Paul Rubin http://[EMAIL PROTECTED] wrote: thebjorn [EMAIL PROTECTED] writes: If the lists are long enough to care, either rewrite use a set-based solution if the items are hashable, or keep the elements sorted and rewrite to use the bisect module if the elements can be ordered. Well, you want a tree data structure to have fast insertions to remember what items have already been seen. There's been a bunch of proposals for an ordered dict type that works like this. Some day... Amen! .. *sigh*... -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Terry Reedy wrote: Jeff Schwab [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] [snip discussion of 'with' statements] | Yes, this seems to be the Python way: For each popular feature of some | other language, create a less flexible Python feature that achieves the | same effect in the most common cases (e.g. lambda to imitate function | literals, or recursive assignment to allow x = y = z). This is a rather acute observation. Another example is generators versus full coroutines (or continuations). Guido is content to capture 80% of the practical use cases of a feature. He never intended Python to be a 100% replace-everything language. I think the idea is to balance power on one hand, against complexity and potential confusion on the other. One great thing about C is that a programmer can realistically hope to know the entire language definition; maybe Guido would like the same to be true of Python. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote:
Terry Reedy [EMAIL PROTECTED] writes:
| Yes, this seems to be the Python way: For each popular feature of some
| other language, create a less flexible Python feature that achieves the
| same effect in the most common cases (e.g. lambda to imitate function
| literals, or recursive assignment to allow x = y = z).
This is a rather acute observation. Another example is generators versus
full coroutines (or continuations). Guido is content to capture 80% of the
practical use cases of a feature. He never intended Python to be a 100%
replace-everything language.
I don't understand the lambda example due to not being sure what Jeff
means by function literals. But in other languages, lambda is the
basic primitive, and def or equivalent is syntax sugar.
Sorry, I didn't know what else to call them except lambdas. I meant
the bare code blocks you can use in Perl, or what Java tries to achieve
via anonymous inner classes. So to use the Perl example: If you want
to sort a list using some arbitrary snippet of code as the comparison
function, you can write:
sort { code to compare $a and $b } @elements
This isn't really native in C++ either:
http://www.boost.org/doc/html/lambda.html
What language do you have in mind, in which lambda is more basic than
named definitions? Are you coming from a functional language background?
--
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Re: Hyphenation module PyHyphen-0.3 released
thebjorn [EMAIL PROTECTED] wrote: Visual Studio 2003 was not found on this system. If you have Cygwin installed, you can try compiling with MingW32, by passing -c mingw32 to setup.py. -- bjorn You need to convince MingW to use the correct VS runtime. Cribbing from: http://www.develer.com/oss/GccWinBinaries the easy way to do this might be to find(in your mingw /lib directory) and copy or rename libmsvcr71.a and libmsvcr71d.a into libmsvcrt.a and libmsvcrtd.a (backing up the originals if desired). If the MingW you have installed doesn't provide the appropriate runtime, you would have to track that down. The MingW/GCC package from the linked page provides a utility to do this, but it is a tossup/up to you if the version of GCC provided is suitable for 'production' use. max -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes: One great thing about C is that a programmer can realistically hope to know the entire language definition; maybe Guido would like the same to be true of Python. C is horrendously complicated, with zillions of obscure traps. C++ is even worse; there's actually a published book specifically about C++ pitfalls. Python is underspecified but freer of weird hazards in practice. C and C++ should practically be outlawed at this point. -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes:
So to use the Perl example: If you want to sort a list using some
arbitrary snippet of code as the comparison function, you can write:
sort { code to compare $a and $b } @elements
Yes, you can do that in Python, using a lambda expression, a named
function, or whatever.
What language do you have in mind, in which lambda is more basic than
named definitions? Are you coming from a functional language
background?
All languages that I know of with lambda, treat it as more basic than
named definitions, e.g. the Lisp family (not sure if those count as
functional languages) in addition to functional languages like Haskell.
--
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Re: Article of interest: Python pros/cons for the enterprise
Matthew Woodcraft wrote:
Jeff Schwab [EMAIL PROTECTED] wrote:
Matthew Woodcraft wrote:
Jeff Schwab [EMAIL PROTECTED] wrote:
The most traditional, easiest way to open a file in C++ is to use an
fstream object, so the file is guaranteed to be closed when the fstream
goes out of scope.
Out of interest, what is the usual way to manage errors that the
operating system reports when it closes the file?
By default, the fstream object just sets its failbit, which you can
check manually by calling my_stream.fail(). If you want anything
particular to take place on failure to close a stream, you either have
to call close manually, or you need a dedicated object whose destructor
will deal with it.
Alternatively, you can tell the fstream ahead of time that you want
exceptions thrown if particular actions fail. There's a convention that
destructors don't ever throw exceptions, though, so it would be unusual
to request an exception when close() fails.
I see. Then, unless you don't care about data loss passing silently,
this 'most traditional' way to open a file is unsuitable for files
opened for writing.
No, why would you think so? If you want something special to happen
when the close() fails (as you indeed would if you were writing
important data), you have to say somehow that you want your special code
called. What syntax would you like to see? Here's what the C++ would
look like, supposing you have a type LoggingCloser that calls close and
logs any failure:
void f(std::string file_name) {
std::ofstream out(file_name.c_str()); // [1]
LoggingCloser closer(out);
// ... your work code here ...
}
The closer's destructor is guaranteed to be called before the file
stream's. That gives it a chance to call close manually, and keeps the
error-handling code separate from the rest of the program logic.
Compare the following Python equivalent, assuming we've replaced Logging
Closer's constructor and destructor with __enter__ and __exit__ definitions:
def f(file_name):
with file(file_name, 'w') as out:
with LoggingCloser(out) as closer:
// ... your work code here ...
In this case, the Python with-statement is not too bad, because you only
have two constructor/destructor pairs. For each new pair, though, it
seems like you need an extra level of nesting (and therefore
indentation). Of course, it may just be that I don't yet know how to
use the with-statement effectively.
[1] That c_str() kludge is usually the primary complaint about using
ofstream. It has been fixed in the new draft standard, which will
become official in 2009.
--
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RE: Hyphenation module PyHyphen-0.3 released
On Behalf Of Max Erickson
the easy way to do this might be to find(in your mingw /lib
directory) and copy or rename libmsvcr71.a and libmsvcr71d.a
into libmsvcrt.a and libmsvcrtd.a (backing up the originals
if desired). If the MingW you have installed doesn't provide
the appropriate runtime, you would have to track that down.
Here's another way. Go to /MinGW/lib/gcc/mingw32/3.4.2/spec, and modify the
libgcc directive as follows:
*libgcc:
%{mthreads:-lmingwthrd} -lmingw32 -lgcc -lmoldname -lmingwex -lmsvcr71
Regards,
Ryan Ginstrom
--
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Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote:
Jeff Schwab [EMAIL PROTECTED] writes:
So to use the Perl example: If you want to sort a list using some
arbitrary snippet of code as the comparison function, you can write:
sort { code to compare $a and $b } @elements
Yes, you can do that in Python, using a lambda expression, a named
function, or whatever.
You can indeed. I think you can also use this to do the other stuff you
would expect, e.g. return locally defined code snippets to define closures:
def mkadder(n):
return lambda x: x + n
I have gotten the impression that this was somehow inferior in Python
though, at least in terms of performance. Every time somebody uses
lambda here, they seem to get a bunch why are you using lambda?
responses. If I am grossly mistake, please just enlighten me.
What language do you have in mind, in which lambda is more basic than
named definitions? Are you coming from a functional language
background?
All languages that I know of with lambda, treat it as more basic than
named definitions, e.g. the Lisp family (not sure if those count as
functional languages) in addition to functional languages like Haskell.
I note from your other posts that you seem to have a strong Lisp bent.
Lisp programmer and Smalltalk programmers stand out in the crowd. I
first noted this when somebody found a while-loop offensive, on the
grounds that recursion was somehow a more natural way to implement
looping. It can take a while to convince somebody like that they
different idioms work best in different languages.
--
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Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote: Jeff Schwab [EMAIL PROTECTED] writes: One great thing about C is that a programmer can realistically hope to know the entire language definition; maybe Guido would like the same to be true of Python. C is horrendously complicated, with zillions of obscure traps. C++ is even worse; Who feeds you this stuff? there's actually a published book specifically about C++ pitfalls. Mercy, a whole book? My current favorite book of language-specific pitfalls: http://www.javapuzzlers.com/ Wait a few years. A Python Puzzlers book will surely be on the shelves eventually. Here are some of the top results when Googling python pitfalls: http://zephyrfalcon.org/labs/python_pitfalls.html http://evanjones.ca/python-pitfall-scope.html Maybe C++ needs better pub. The guy who wrote the first of those articles says elswhere on his web site: My Python pitfalls article seems to be a popular read. It's written from a somewhat negative viewpoint: things that can go wrong. (Of course, that's useful; you're never going to do these things wrong again. Right? ;-) To counter-balance this, I think there should an article with a more positive viewpoint as well. So I was wondering, if I could collect 10 anti-pitfalls; parts of the Python language that are especially clever, elegant and intuitive. Good luck with that. Once language Y comes along, there will be a million reasons people believe that language X was downright unusable. Python is underspecified but freer of weird hazards in practice. C and C++ should practically be outlawed at this point. On what grounds? I don't approve of the programming language you're using. Cease and desist. Nyah! -- http://mail.python.org/mailman/listinfo/python-list
Re: Tkinter: Missing the last piece of the puzzle
On Feb 23, 9:00 am, [EMAIL PROTECTED] wrote: I have a simple editor built into my visual parser. It has a File menu with typical New, Open, Save, Save As ... options. I now know how to set the options [en/dis]abled and how to check the Text widget's modified flag. Now I want to [en/dis]able those options. Can I ask the text to notify me when the modified flag changes? yes! check out http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/464635 HTH, ~Simon Can I set the statuses when the user clicks File, before the options are displayed? Do I need to create a checker on an independent thread that looks at the flag every few millis? (Tkinter deserves more respect. I've got a good-looking application growing quickly.) -- http://mail.python.org/mailman/listinfo/python-list
Re: @synchronized dect'r c.
On Feb 23, 7:47 pm, [EMAIL PROTECTED] wrote: On Feb 23, 6:19 pm, Paul McGuire [EMAIL PROTECTED] wrote: On Feb 23, 2:03 pm, [EMAIL PROTECTED] wrote: 1) [EMAIL PROTECTED] @synchronized def function( arg ): behavior() Synchronized prevents usage from more than one caller at once: look up the function in a hash, acquire its lock, and call. def synchronized( func ): def presynch( *ar, **kwar ): with _synchlock: lock= _synchhash.setdefault( func, allocate_lock() ) with lock: return func( *ar, **kwar ) return presynch No need for a global _synchhash, just hang the function lock on the function itself: def synch(f): f._synchLock = Lock() def synchedFn(*args, **kwargs): with f._synchLock: f(*args, **kwargs) return synchedFn You might also look at the PythonDecoratorLibrary page of the Python wiki, there is a synchronization decorator there that allows the function caller to specify its own lock object (in case a single lock should be shared across multiple functions). -- Paul- Hide quoted text - - Show quoted text - Why not just: def synched( f ): l= Lock() def presynched( *a, **kwa ): with l: return f( *a, **kwa ) It's not like the lock is ever used anywhere else. Besides, if it is, isn't the correct spelling: class Asynched: def __init__( self, func ): self.func, self.lock= func, Lock() def __call__( self, *a, **kwa ): return self.func( *a, **kwa ) and def synched( func ): return Asynched( func ) or even synched= Asynched ?- Hide quoted text - - Show quoted text - So, you live around here? Where'd you park? ;) -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes: def mkadder(n): return lambda x: x + n I have gotten the impression that this was somehow inferior in Python though, at least in terms of performance. Every time somebody uses lambda here, they seem to get a bunch why are you using lambda? responses. If I am grossly mistake, please just enlighten me. There are some Python users who object to lambda on stylistic grounds, and would rather that you say def mkdadder(n): def adder(x, n): return x + n return adder Those same users tend to object to higher-order functions (preferring listcomps or genexps). It seems to me though that Python is moving more towards HOF-oriented styles because of the utility of HOF's over iterators (look at itertools). That might make its learning curve steeper for beginners; I don't have a good sense of this. I note from your other posts that you seem to have a strong Lisp bent. Lisp programmer and Smalltalk programmers stand out in the crowd. I first noted this when somebody found a while-loop offensive, on the grounds that recursion was somehow a more natural way to implement looping. It can take a while to convince somebody like that they different idioms work best in different languages. Well, the saying is to iterate is human; to recurse, divine ;-). Scheme has while-loops but they are just syntax sugar for recursion. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a open souce IDE writen by C( C++) or partly writen by C( C++)?
On Feb 24, 6:48 am, Ricardo Aráoz [EMAIL PROTECTED] wrote: Lie wrote: On Feb 23, 4:02 pm, zaley [EMAIL PROTECTED] wrote: On Feb 22, 11:06 pm, Jesper polluks(#at#)post.tele.dk wrote: Give PyScripter fromhttp://www.mmm-experts.com/atry It is for Windows, though it is written in Delphi and not in C/C++ /Jesper zaley [EMAIL PROTECTED] skrev i en meddelelsenews:[EMAIL PROTECTED] Of course, python scripts debugger On 2ÔÂ22ÈÕ, ÏÂÎç3ʱ22·Ö, zaley [EMAIL PROTECTED] wrote: My project need a simple scripts debugger . I hope I can find something instructive Stefan Behnel дµÀ£º zaley wrote: Is there a open souce IDE writen by C( C++) or partly writen by C( C+ +)? Tons of them. What do you want to do with it? Stefan- Hide quoted text - - Show quoted text - But PyScripter is not a open source project Am I correct to say that the reason why you wanted an open source C++ IDE is because you wanted the freedom to modify your own programming environment? From the About window in PyScripter : A freeware, open source Python scripter integrated development environment created with the ambition to bring to the Python community the quality and functionality available in commercial IDEs available for other languages. So I think we could say PyScripter IS an open source project.- Hide quoted text - - Show quoted text - Really, what I want to do is that scripts can be executed step by step . I know By Py_Runstring clauses in main function can executed by step . But I can't know how to step into a function and how to step in a function. So I hope I can find something helpful in open source IDE for python. -- http://mail.python.org/mailman/listinfo/python-list
Official IRC channel for Python?
Howdy, I was wondering if there's official IRC channel for Python. I tried #python irc.freenode.net and irc.openproject.net with no luck. Could you please give me some suggestions? -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes: there's actually a published book specifically about C++ pitfalls. Mercy, a whole book? http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?EAN=9780201179286 C and C++ should practically be outlawed at this point. On what grounds? I don't approve of the programming language you're using. Cease and desist. Nyah! Well, outlawed of course is a figure of speech; however use of those languages should be a red flag in a design review, and a factor in determining product liability if a program misbehaves. Think of all the buffer overflow exploits against Microsoft Windows programs that couldn't have happened if Microsoft had used safer languages. There was clearly a failure to use best engineering practices. -- http://mail.python.org/mailman/listinfo/python-list
Re: Official IRC channel for Python?
js [EMAIL PROTECTED] writes: I tried #python irc.freenode.net That has always worked for me. -- http://mail.python.org/mailman/listinfo/python-list
PHP Developer highly interested in Python (web development) with some open questions...
Hi! My brother is dreaming and dying for python and swear that it is the ultimate killer application language. I am coding Webapplication in PHP5 and ask myself if for python are: - application frameworks like: Zend Framework and ezComponents - What is the Zope Applikation Server? Is it also a Webserver like the Apache or Tomcat Webserver? - Is there a way of Round Tripp engineering based on UML XMI Files to generate python files (with it's dependencies) - Let us assume, I want to write a Web application in Python (what I did now in PHP5) and want to distribute my work under commercial usage. Can I encrypt my work and generate Licence Files for Customers who would purchase my End-Sollution like with: - Zend Encoder - IonCube - SourceGuardian ??? I just ask, because I have finished a product and will encrpyt it with the Ioncube encoder based on PHP5. for answering all my Questions, I would thank you guys very much Tamer Higazi -- http://mail.python.org/mailman/listinfo/python-list
Seeing locals() from imported function
I apologize for this very basic question, but I can't understand how
this works...
I want to import a function from module B into my main script A, so
this function can see and use the locals from A.
For example:
def auto():
urls = ['/', 'index']
for k,v in __main__.locals().items(): # these locals
are the ones of the main script
if isinstance(v,type) and k != 'index':
urls.append('/%s' %k)
urls.append(k)
return tuple(urls)
Of course this doesn't work...
Any hint?
Luis
--
http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Paul Rubin wrote: Jeff Schwab [EMAIL PROTECTED] writes: there's actually a published book specifically about C++ pitfalls. Mercy, a whole book? http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?EAN=9780201179286 C and C++ should practically be outlawed at this point. On what grounds? I don't approve of the programming language you're using. Cease and desist. Nyah! Well, outlawed of course is a figure of speech; however use of those languages should be a red flag in a design review, and a factor in determining product liability if a program misbehaves. Your product gets the benefit of the doubt if it was written in Python, but not if written in C? What if the Python interpreter screws up? Think of all the buffer overflow exploits against Microsoft Windows programs that couldn't have happened if Microsoft had used safer languages. There was clearly a failure to use best engineering practices. In the first place, you're not distinguishing C from C++. I know you think they're the same. They're not. Python's array bounds checking is done in C, as is the case for traditional OS kernels. C++, like Python, offers you container types that smell like arrays, but do safety checking under the hood; the C++ bounds checks, unlike the Python checks, are done in-language. If C++ were marketed like Java, people might advertise that the C++ standard containers are pure C++, or that C++ is written in C++. Secondly, you're going to have a hard time writing an operating system kernel without fixed-size buffers. You have to read data in chunks of some size. It's fine to say that buffer access should be checked to make sure indexes should be in range, but somebody actually has to write the code to do the checking, and then programmers have to use it. Buffer overflows are the result of developers deliberately choosing not to use bounds-checking. In Python, somebody could still define a monolithic array, use different parts of it to represent different things, and then oops lose track of their index, thereby overwriting one part of the array with data that should have stayed in the other part. If you're thinking Yeah, they *could*, but only a dodo would do that, and it's not Python's fault that the programmer did something bone-headed, then you're beginning to get the picture. If you somehow wrote an OS kernel in Python, and the above-mentioned bone-headedness took place, then there would be no lower level to save your OS from having a dangerous security hole. Even if the hardware supported checked access for large quantities of arbitrarily sized arrays, somebody would have to enable that access. Even then you're trusting the hardware developers to check for invalid indexes (bus errors and seg faults). Should we outlaw computer hardware, too? Thirdly, you mentioned a failure to use best engineering practices. If you mean there was a failure to design and implement a bug-free operating system, then by Jiminy, you're right. Best practices, though, is usually just what managers say when they mean what everybody else is doing. The idea is that if you're a manager who sticks to best practices, then if everything goes to hell, the problem can't be linked specifically to you. Server-side Python is now, at this very moment, becoming acceptable as best practice. It's no better or worse for this; it's just that a lot more uninspired, uncreative programmers are about to start using it. Do not underestimate their ability to make any programming language look bad. If you make it fool-proof, they'll build a better fool. The only way to keep them from writing code that will blow up at run-time is to impose formal verification of their program, every time they change it; that's what the C++ static type system lets you do, in a limited and easily subverted way. Even if you could somehow remove every feature open to potential abuse, and thereby dodo-proof the language, the result would be a slow, weak, ugly language that non-dodos would not want to use. But hey, at least it would still be best practice. -- http://mail.python.org/mailman/listinfo/python-list
Re: Official IRC channel for Python?
Really? maybe I'm been blocked from it... thanks. On 23 Feb 2008 20:37:42 -0800, Paul Rubin http://phr.cx@nospam.invalid wrote: js [EMAIL PROTECTED] writes: I tried #python irc.freenode.net That has always worked for me. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
PHP Developer highly interested in Python (web development) with some open questions...
Hi! My brother is dreaming and dying for python and swear that it is the ultimate killer application language. I am coding Webapplication in PHP5 and ask myself if for python are: - application frameworks like: Zend Framework and ezComponents - What is the Zope Applikation Server? Is it also a Webserver like the Apache or Tomcat Webserver? - Is there a way of Round Tripp engineering based on UML XMI Files to generate python files (with it's dependencies) - Let us assume, I want to write a Web application in Python (what I did now in PHP5) and want to distribute my work under commercial usage. Can I encrypt my work and generate Licence Files for Customers who would purchase my End-Sollution like with: - Zend Encoder - IonCube - SourceGuardian ??? I just ask, because I have finished a product and will encrpyt it with the Ioncube encoder based on PHP5. for answering all my Questions, I would thank you guys very much. Tamer Higazi -- http://mail.python.org/mailman/listinfo/python-list
Re: Official IRC channel for Python?
js wrote: Really? maybe I'm been blocked from it... thanks. Currently 479 users. Have you been blocked from many channels? regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Article of interest: Python pros/cons for the enterprise
Jeff Schwab [EMAIL PROTECTED] writes: languages should be a red flag in a design review, and a factor in determining product liability if a program misbehaves. Your product gets the benefit of the doubt if it was written in Python, but not if written in C? What if the Python interpreter screws up? The Python interpreter has been run in production for over a decade modulo comparatively small incremental changes, heavily reviewed and tested by multiple people, between versions. It's likely to be more reliable than any one-off C program of comparable size. Further, for a C application, the analogous situation to the Python interpreter screwing up would be the C compiler screwing up (generating wrong code). They have that possibility in common. But for the C application, the screwup can be in two places (the compiler or the application) while Python limits it to one place. The principle here is to minimize the size of the so-called trusted codebase. Either way, the ongoing effort (PyPy) to write Python in Python will probably improve Python's reliability. In the first place, you're not distinguishing C from C++. I know you think they're the same. They're not. Python's array bounds checking is done in C, as is the case for traditional OS kernels. C++, like Python, offers you container types that smell like arrays, but do safety checking under the hood; Not as long as you can have pointers to those objects that contain naked memory addresses which can be invalid. Buffer overflows are the result of developers deliberately choosing not to use bounds-checking. Yes, the most common way that choice is expressed is by choosing to code in C or C++ in the first place. to enable that access. Even then you're trusting the hardware developers to check for invalid indexes (bus errors and seg faults). Should we outlaw computer hardware, too? Again, the concept is best practices which is an engineering term, not a mathematical one. Best practices are not infallible, they're just the best normal practices observed in real-world projects of similar scope. Best practices, though, is usually just what managers say when they mean what everybody else is doing. No really, among other things it includes following standards that are designed by people who know what they're doing. That actually means something. The idea is that if you're a manager who sticks to best practices, then if everything goes to hell, the problem can't be linked specifically to you. That is a very valuable aspect. If I'm writing an encryption program, best practice is to use a standard algorithm like AES instead of concocting my own algorithm. If something does turn out to be wrong wtih AES that makes my program fail, I'm very glad to be able to point to the rigorous standardization process that AES went through and say that I made the best choice I could with available information. If for some reason I think there's an 0.002% chance that something is wrong with AES but only an 0.001% chance that something is wrong with my home-cooked algorithm, AES is still the obvious choice. Same thing with internet applications, I'm much better off writing in a type-safe language than relying on the intricacies of my unique application code to behave properly in a language without type-safety. The only way to keep them from writing code that will blow up at run-time is to impose formal verification of their program, every time they change it; that's what the C++ static type system lets you do, in a limited and easily subverted way. Why not get rid of the limitations and easy subversions? And I can't agree that using a basic type like int x[10]; is somehow a subversion. Subversion means you have to go to some lengths to break the type safety. Even if you could somehow remove every feature open to potential abuse, and thereby dodo-proof the language, the result would be a slow, weak, ugly language that non-dodos would not want to use. But hey, at least it would still be best practice. Enforcing type safety is certainly an enormous step towards dodo-proofing a language, it hugely helps the reliability of real programs, and is one of the reasons Python and Java are displacing C++. -- http://mail.python.org/mailman/listinfo/python-list
