Re: What is a type error?
Joachim Durchholz wrote:
Marshall schrieb:
Joachim Durchholz wrote:
Chris Smith schrieb:
For example, I wrote that example using variables of type int. If we
were to suppose that we were actually working with variables of type
Person, then things get a little more complicated. We would need a few
(infinite classes of) derived subtypes of Person that further constrain
the possible values for state. For example, we'd need types like:
Person{age:{18..29}}
But this starts to look bad, because we used to have this nice
property called encapsulation. To work around that, we'd need to
make one of a few choices: [...] (c) invent some kind of generic
constraint language so that constraints like this could be expressed
without exposing field names. [...] Choice (c), though, looks a
little daunting.
That's not too difficult.
Start with boolean expressions.
If you need to check everything statically, add enough constraints that
they become decidable.
I'm not sure I understand. Could you elaborate?
Preconditions/postconditions can express anything you want, and they are
an absolutely natural extensions of what's commonly called a type
(actually the more powerful type systems have quite a broad overlap with
assertions).
I'd essentially want to have an assertion language, with primitives for
type expressions.
Now, I'm not fully up to speed on DBC. The contract specifications,
these are specified statically, but checked dynamically, is that
right? In other words, we can consider contracts in light of
inheritance, but the actual verification and checking happens
at runtime, yes?
Wouldn't it be possible to do them at compile time? (Although
this raises decidability issues.) Mightn't it also be possible to
leave it up to the programmer whether a given contract
was compile-time or runtime?
I've been wondering about this for a while.
Marshall
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Re: Accessors in Python (getters and setters)
Bruno Desthuilliers wrote: I decided to change the name of an attribute. Problem is I've used the attribute in several places spanning thousands of lines of code. If I had encapsulated the attribute via an accessor, I wouldn't need to do an unreliable and tedious search and replace find and grep are usually mostly reliable for this kind of tasks. you mean sed :) sed 's/oldName/newName/g' oldFile newFile -- Under construction -- http://mail.python.org/mailman/listinfo/python-list
Re: threading troubles
sreekant wrote: Hi folks What am I doing wrong in the following? I just want to run fluidsynth in the background. Others have pointed you at os.popen. In non-crippled languages, use processes (e.g. popen) when you wish to preserve the years of hard work that OS designers put into protected memory. Use threads only when you know why you want to abandon such and share all memory. 95% or more of the time when you're making the multiprocessing decision, threads are the wrong choice. 5% (or less) of the time they're indispensable. But if you're just looking for asychronous processing and don't know why you need to abandon memory protection, go with processes. -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib2 on Windows Vista
Sriram Krishnan wrote: I'm running Python 2.4.3 on Windows Vista June CTP. I'm not able to open any site using the urllib2 and related family of modules I think you need to break the error further down. Try httplib instead of urllib, and see what connect does. Then break this down into socket calls (reading the source of httplib.connect, and executing it manually in single-stepping), so that you know what the precise arguments passed to getaddrinfo are. FWIW, 11001 is WSAHOST_NOT_FOUND, which suggests that you have DNS configured incorrectly. Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: threading troubles
sreekant [EMAIL PROTECTED] (S) wrote:
S Hi folks
S What am I doing wrong in the following? I just want to run fluidsynth in
S the background.
S #
S class MyThread(threading.Thread):
S def __init__(self, cmd, callback):
S self.__cmd = cmd
S self.__callback = callback
S threading.Thread.__init__(self)
S def run(self):
S os.system(self.__cmd)
S self.__callback('abcd')
S return
S cmd=midiplay+' '+fmidi
S xc=MyThread(cmd,addlog)
S xc.start()
S ##
S midiplay is 'fluidsynth -ni /home/mysndfont.sf2 mymidi.mid'
S addlog is a function which prints the log.
S If I run it only with xc.start() it does not run the program as in
S os.system. However if I put
S xc.start()
S xc.run()
S then it starts and runs it in foreground with my pygtk ui non responsive.
You shouldn't call run() yourself. It is for the thread library itself.
I tried your example with cmd='ls -l' and it works. If I put a print
'started' after the xc.start(), it prints that before the output of ls -l,
indicating that ls -l is running in the background. (Of course the actual
order is up to the scheduler.) Maybe running it inside a pygtk program
could be different but I wouldn't know why.
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URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4]
Private email: [EMAIL PROTECTED]
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Re: document
Please send me an anti-virus version. I can not read your attacked file!python-list@python.org wrote: Please read the document. Want to be your own boss? Learn how on Yahoo! Small Business. -- http://mail.python.org/mailman/listinfo/python-list
Re: Detecting 64bit vs. 32bit Linux
In article [EMAIL PROTECTED], Robin Becker [EMAIL PROTECTED] wrote: Michael Yanowitz wrote: .. I need to detect whether the operating system I am running on (not the Python version) is 64bit or 32bit. One requirement is that I need to include support for non-Intel/AMD architectures. The standard C way would be to check sizeof(void *). so on those old ARM RISC OSes with 32 bit arithmetic would I get sizeof(void *) == 4 when the address bus was 26 bits wide? And the original 68000-based Macs where you would get the same sizeof(void *), but the address bus was only 24 bits wide. Nevertheless, you were supposed to pretend that addresses were a full 32 bits in size. The programs that didn't got into trouble later. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python for modem App
Any Idea !!!??? --- First Iranian Python Programming Community -- www.Python.ir -- http://mail.python.org/mailman/listinfo/python-list
Re: language design question
Bryan wrote: and how do you make sure that everything subclasses this base class ? in this hypothetical case, i was assuming len() would be put in object and every class subclasses object implicitly or explicitly (ie, new style classes only). if it was done that way, would len(obj) == obj.len() in all cases? why should *everything* be forced to have a length ? /F -- http://mail.python.org/mailman/listinfo/python-list
How to terminate a main script?
Hi, I'm still looking for an elegant and clear means to terminate the main script in Python. Unfortunately, Python doesn't allow a 'return' instruction in the main script. Using sys.exit(0) produces an error message which looks dangerous to an uninitiated user. The same is true for an exception. And setting a 'flag' and testing at several place for 'fall through' is ugly and error-prone. So what is a good choice? Many thanks for a hint, Helmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessors in Python (getters and setters)
ZeD wrote:
Bruno Desthuilliers wrote:
I decided to change the name of an attribute. Problem is I've used the
attribute in several places spanning thousands of lines of code. If I
had encapsulated the attribute via an accessor, I wouldn't need to do
an unreliable and tedious search and replace
find and grep are usually mostly reliable for this kind of tasks.
you mean sed :)
No, I meant find and grep.
sed 's/oldName/newName/g' oldFile newFile
Yeah, fine - as long as your pretty sure the same name is not used in
other contexts in any of the source files...
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p in '[EMAIL PROTECTED]'.split('@')])
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Re: mod_python fails to load under wamp
I suggest you search the download files on Xampp's sourceforge site and look for an older version with Apache 2.0.55 . I'm not sure, but I think xampp version 1.5.1 will be ok I did this just a few days ago, you could be right, but version 1.5.1 had no release notes, and a dodgy release number (151), so I thought it safer to go for 1.5.0 which definitely has Apache 2.0.55 (1.5.2 has version 2.2.something), and people were concentrating harder when it was released ;-). -- http://mail.python.org/mailman/listinfo/python-list
Re: How to terminate a main script?
Helmut Jarausch wrote: Using sys.exit(0) produces an error message which looks dangerous to an uninitiated user. sys.exit(0) doesn't print anything at all. $ python import sys sys.exit(0) $ however, sys.exit() raises an exception to tell the runtime that it wants to terminate the program, so if you're using a catch-all exception handler that treats all exceptions as dangerous errors, it'll look like a dangerous error too. the solution is simple: don't do that. instead of writing: try: ... except: print OMG! Ponies! write try: ... except (SystemExit, KeyboardInterupt): raise except: print OMG! Ponies! /F -- http://mail.python.org/mailman/listinfo/python-list
Re: mod_python fails to load under wamp
Uh... this may sound silly, but aren't .so files UNIX/Linux/Solaris shared object files... Yes, but apache uses them (or at least the same file extension) for modules on Windows and Linux, so mod_python.so is correct. -- http://mail.python.org/mailman/listinfo/python-list
Re: free python hosting !
Bayazee wrote:
hi
i want a free hosting for python .
Then setting up your own hosting might be a good solution - if you can
have a decent internet connection.
www.python.ir -- Persian Python Community !
I'm afraid I won't be able to contribute !-)
--
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p in '[EMAIL PROTECTED]'.split('@')])
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Re: threading troubles
I decided in the end to use fork and all is well. Thanks sree -- http://mail.python.org/mailman/listinfo/python-list
How to use images at the bachground?
hi all, how to get out of the python shell which is executing a command? how to use images in the background of a page in Tkinter? -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
iapain wrote: No, I cant change permission or delete the module, the best would be something to detect 'import os' in user code .. trust me, implementing a restricted execution model for Python that actually works is a *lot* harder than that. googling for python restricted execution might give you some clues. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: help a newbie with a IDE/book combination
[EMAIL PROTECTED] wrote:
Hi,
I already have a couple of newbie books on Python itself, but would
rather get started with a nice to use IDE and I am therefore looking
for a good IDE to learn Python. On my computer I have installed eric
(http://ericide.python-hosting.com/) but it lacks any kind of useful
documentation on its use.
Is there a good IDE which would be well documented out there?
imho
You really don't need a full blown IDE to learn Python - any decent code
editor will do. Learning to use an IDE can take some time (even with a
good documentation), and you'll probably have more clues wrt/ IDE
choice/usage once you'll know at least the language basics.
Also, there's a problem with language-specific IDEs: you have to learn a
new IDE for each language. A good, extensible code editor (emacs, Vim,
etc) can be a better solution if you use different languages.
/imho
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p in '[EMAIL PROTECTED]'.split('@')])
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Re: What is a type error?
David Hopwood wrote: Yes, I'm well aware that most of this thread has been off-topic for c.l.p.m, but it is no less off-topic for the other groups (except possibly c.l.functional), and I can't trim the Newsgroups line down to nothing. is someone forcing your to post off-topic stuff against your will? sounds scary. do you want us to call the police? /F -- http://mail.python.org/mailman/listinfo/python-list
Re: How to terminate a main script?
Helmut Jarausch [EMAIL PROTECTED] writes: Using sys.exit(0) produces an error message which looks dangerous to an uninitiated user. What message? Your program should exit silently when you call sys.exit(0). Ganesan -- Ganesan Rajagopal -- http://mail.python.org/mailman/listinfo/python-list
Re: function that modifies a string
I'm sorry, perhaps I'm being slow today, but just why are they dangerous? More dangerous than, say, mutable lists and mutable dicts? Unless I'm missing something, the worst that can happen is that people will write inefficient code, and they'll be caught out by the same sort of things that surprise newbies about lists. E.g. using a list as a default value in function definitions. Well, they certainly aren't more dangerous than other mutable objects in python. But in comparison to only dealing with immutable collections, using immutable strings never made something impossible or even hard to do - at least for me. Sometimes a bit harder to do efficiently. So - the overall danger of mutability can be avoided with immutable strings pretty neat, and thus one should (or could) go without them. Regards, Diez -- http://mail.python.org/mailman/listinfo/python-list
Making HTTP requests using Twisted
I'm hoping to write a program that will read any number of urls from stdin (1 per line), download them, and process them. So far my script (below) works well for small numbers of urls. However, it does not scale to more than 200 urls or so, because it issues HTTP requests for all of the urls simultaneously, and terminates after 25 seconds. Ideally, I'd like this script to download at most 50 pages in parallel, and to time out if and only if any HTTP request is not answered in 3 seconds. What changes do I need to make? Is Twisted the best library for me to be using? I do like Twisted, but it seems more suited to batch mode operations. Is there some way that I could continue registering url requests while the reactor is running? Is there a way to specify a time out per page request, rather than for a batch of pages requests? Thanks! #- from twisted.internet import reactor from twisted.web import client import re, urllib, sys, time def extract(html): #do some processing on html, writing to stdout def printError(failure): print sys.stderr, Error:, failure.getErrorMessage( ) def stopReactor(): print Now stopping reactor... reactor.stop() for url in sys.stdin: url = url.rstrip() client.getPage(url).addCallback(extract).addErrback(printError) reactor.callLater(25, stopReactor) reactor.run() -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Chris Smith [EMAIL PROTECTED] writes:
No what happens if right here you code
b := 16;
Does that again change the type of b? Or is that an illegal
instruction, because b has the local type of (18..22)?
It arranges that the expression b after that line (barring further
changes) has type int{16..16}, which would make the later call to
signContract illegal.
The assignment might be performed in a function called there, so it's
not visible locally.
Propagating constraints from conditionals is not applicable to mutable
variables, at least not easily.
I think that constant bounds are not very useful at all. Most ranges
are not known statically, e.g. a variable can span the size of an
array.
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\__/ [EMAIL PROTECTED]
^^ http://qrnik.knm.org.pl/~qrczak/
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Re: Making HTTP requests using Twisted
rzimerman wrote: I'm hoping to write a program that will read any number of urls from stdin (1 per line), download them, and process them. So far my script (below) works well for small numbers of urls. However, it does not scale to more than 200 urls or so, because it issues HTTP requests for all of the urls simultaneously, and terminates after 25 seconds. Ideally, I'd like this script to download at most 50 pages in parallel, and to time out if and only if any HTTP request is not answered in 3 seconds. What changes do I need to make? Is Twisted the best library for me to be using? I do like Twisted, but it seems more suited to batch mode operations. Is there some way that I could continue registering url requests while the reactor is running? Is there a way to specify a time out per page request, rather than for a batch of pages requests? Have a look at pyCurl. (http://pycurl.sourceforge.net) Regards Sreeram signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Howto or Tutorial for tokenize module for a newbie?
TY wrote: Hi, Can someone point me to a Howto or Tutorial for tokenize module for a newbie? I read the documentation but it doesn't have a lot of info... Here's another useful example : http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52298 All the best, Fuzzyman http://www.voidspace.org.uk/python/index.shtml Thanks! -- http://mail.python.org/mailman/listinfo/python-list
Generating all ordered substrings of a string
Hi, I want to generate all non-empty substrings of a string of length =2. Also, each substring is to be paired with 'string - substring' part and vice versa. Thus, ['abc'] gives me [['a', 'bc'], ['bc', 'a'], ['ab', 'c'], ['c', 'ab'], ['b', 'ac'], ['ac', 'b']] etc. Similarly, 'abcd' should give me [['a', 'bcd'], ['bcd', 'a'], ['abc', 'd'], ['d', 'abc'], ['b', 'acd'], ['acd', 'b'],['c', 'abd'], ['abd', 'c'], ['ab', 'cd'], ['cd', 'ab'], ['bc', 'ad'], ['ad', 'bc'], ['ac', 'bd'],['bd','ac']] I've tried the following but i cant prevent duplicates and i'm missing some substrings: colocn = 'abcd' k = 4 for i in range(k-1): for j in range(1,k): rule1 = [colocn[i:i+j],colocn[:i]+colocn[i+j:]] rule2 = [colocn[:i]+colocn[i+j:],colocn[i:i+j]] rules.append(rule1) rules.append(rule2) rules [['a', 'bcd'], ['bcd', 'a'], ['ab', 'cd'], ['cd', 'ab'], ['abc', 'd'], ['d', 'abc'], ['b', 'acd'], ['acd', 'b'], ['bc', 'ad'], ['ad', 'bc'], ['bcd', 'a'], ['a', 'bcd'], ['c', 'abd'], ['abd', 'c'], ['cd', 'ab'], ['ab', 'cd'], ['cd', 'ab'], ['ab', 'cd']] Any ideas?? TIA, girish This message was sent using IMP, the Internet Messaging Program. -- http://mail.python.org/mailman/listinfo/python-list
Re: language design question
Bryan wrote: Fredrik Lundh wrote: Bryan wrote: could you get the same result by putting these methods in base class object that everything subclasses? and how do you make sure that everything subclasses this base class ? /F in this hypothetical case, i was assuming len() would be put in object and every class subclasses object implicitly or explicitly (ie, new style classes only). if it was done that way, would len(obj) == obj.len() in all cases? isinstance(1, object) True What's 1 . len() ? regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://holdenweb.blogspot.com Recent Ramblings http://del.icio.us/steve.holden -- http://mail.python.org/mailman/listinfo/python-list
Re: Making HTTP requests using Twisted
rzimerman wrote: Is Twisted the best library for me to be using? I do like Twisted, but it seems more suited to batch mode operations. Is there some way that I could continue registering url requests while the reactor is running? Is there a way to specify a time out per page request, rather than for a batch of pages requests? there are probably ways to solve this with Twisted, but in case you want a simpler alternative, you could use Python's standard asyncore module and the stuff described here: http://effbot.org/zone/effnews.htm especially http://effbot.org/zone/effnews-1.htm#storing-the-rss-data http://effbot.org/zone/effnews-3.htm#managing-downloads /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessors in Python (getters and setters)
Hello, Thanks for the responses. The reason I want to change the name of the attribute is because it doesn't reflect the purpose of the attribute, anymore. The attribute was originally a string object, but not anymore. It is primarily a readability issue. There are also a few key attributes I don't want developers, including myself, fiddling with. Properties /accessors are good because they allow you to encapsulate attributes so you can change implementations at will. Some of you have argued I would have needed to change accessor names too if I had misnamed them earlier. It's hard to say. I find myself changing the names of attributes a lot more frequently than I do functions or methods. Choosing a crappy attribute name is effortless for me, especially during intense coding sessions. I usually realize I've choosing a crappy attribute name the next day, sometimes even later. However, I put a lot more effort into choosing method and function names, especially when I know it may likely be a public API. Plus it's really hard to choose crappy accessor name. Regards -- http://mail.python.org/mailman/listinfo/python-list
Re: Looking for a HTML like rendering library (wishlist)
Laszlo Nagy wrote: I'm looking for a library that can do the following: * Parse a simple structured text file (XML or HTML etc.) * Render its output to an image * I would like to give the maximum width of the image (but not the minimum) * I would like to use my custom TrueType fonts, and some basic formatting: colors, underline, numbered and bulleted lists * I would like to embed some PNG (transparent) images, and align them inside the text * The library should be able to calculate the size of the image before rendering * The library should be able to render the image into memory * It should be reasonably fast * It should be independent of windowing toolkits (PIL is okay) Why I need this: create widgets in GUI applications, for example: * A label that can display formatted text * A new grid cell renderer that can display small images and text as well * Hint window (tooltip) that has formatted text and images * Create automatic signatures for e-mails (not GUI related) * etc After reading this, I still do not understand why you want to do this with images. Virtually any GUI toolkit can display text, most can natively display HTML, just look at Qt for a good example. So why not just use the native features? Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: How to use images at the bachground?
hi all, how to get out of the python shell which is executing a command? how to use images in the background of a page in Tkinter? on Unix, ctrl-c or ctrl-d may do the job. on Windows, ctrl-z will do -- http://mail.python.org/mailman/listinfo/python-list
Re: Augument assignment versus regular assignment
On 2006-07-10, Terry Reedy [EMAIL PROTECTED] wrote: Antoon Pardon [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I disagree. The += version only evaluates the index once, but still has to find the object twice. No it does not *have* to find the object twice and no it does *not* find the object twice. From the viewpoint of the interpreter, the purpose of abbreviating 'objectexpression = objectexpression op arg' as 'objectexpression op=arg' is to avoid unnecessary recalculation But is the viewpoint of the interpreter somehow relevant? IMO the question is if the actual behaviour is compatible with what people expect after having read the language reference. The viewpoint of the interpreter IMO doesn't play a role in answering that question. But as far as I can interpret what is happening from the printed lines Your print get/set examples from your black-box testing miss the following key point. While the interpreter still has to *use* the object(s) twice, once to get and once to set, it no longer has to *calculate* the objects twice. The language reference doesn't talk about objects. And IMO you should be carefull if you want to use the word object here. In the line: foo += 1, you can't talk about the object foo, since foo will be bound to a different object after the assignment than it was bound to before. As I read the language reference the x stands for a target expression. Now what does it mean to evaluate a target expression like col[key]. IMO it means finding the location of the item in the collection: the bucket in the directory, the node in the tree ... grosso mode it boils down to the call to __setitem__ or __getitem__ depending on where the col[key] was located in the line (or if you prefer the view from the interpreter it boils down to the BINARY_SUBSCR and STORE_SUBSCR opcodes). So if the language reference seems to implies that col[key] will only be evaluated once in a line like: col[key] += 1 I expect only one call from __setitem__ or __getitem__ (or only one from BINARY_SUBSCR or STORE_SUBSCR) Now I know python doesn't behave this way, but how python actually behave can't be used as an argument that this is the behaviour as described by the language reference. So my question is: suppose I write my own collector, where __setitem__ and __getitem__ have the same side effect. How many times should/will this side effect occur in code like col[key] += 1. As I read the language reference it should happen only once, however that is not what happens. So if the actual behaviour of python is what we want, which is what I suspect, then the language reference should clarify more what the supposed behaviour should be. Now my reading of the language reference can be faulty, but if you want to argue that, I would appreciate it if you could explain how I have to read the language reference in order to come to the conclusion that the side effect in this example has to happen twice. And even in this case would I suggest that the language reference would better be made clearer, since I doubt that I'm the only who will read the language reference this way. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: How to terminate a main script?
Fredrik Lundh wrote: Helmut Jarausch wrote: Using sys.exit(0) produces an error message which looks dangerous to an uninitiated user. sys.exit(0) doesn't print anything at all. Yes, sorry, I was trying in in 'idle' There you get Traceback (most recent call last): File pyshell#1, line 1, in -toplevel- sys.exit(0) SystemExit: 0 -- Helmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany -- http://mail.python.org/mailman/listinfo/python-list
Re: Global except condition
Ernesto wrote: Within the scope of one Python file (say myFile.py), I'd like to print a message on ANY exception that occurs in THAT file, dependent on a condition. Here's the pseudocode: if anyExceptionOccurs(): if myCondition: print Here's my global exception message Is this functionality possible in python? If so, how? What if your module defines a function, and then that function is called from some other module and raises an exception. Would you then want the global exception message to appear? If so then I'm not sure that what you want is possible. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://holdenweb.blogspot.com Recent Ramblings http://del.icio.us/steve.holden -- http://mail.python.org/mailman/listinfo/python-list
Re: Global except condition
Ernesto wrote: Within the scope of one Python file (say myFile.py), I'd like to print a message on ANY exception that occurs in THAT file, dependent on a condition. condition = True def handle_any_exception(function): def trampoline(*args, **kwargs): try: return function(*args, **kwargs) except: if not condition: raise print exception caught in, function.__name__ return n/a # default return value return trampoline @handle_any_exception def myfunc(x): return 1 / x @handle_any_exception def myotherfunc(filename): return open(filename) class MyClass: @handle_any_exception def mymethod(self): raise ValueError(oops) myfunc(1) myfunc(0) myotherfunc(hello.txt) MyClass().mymethod() /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessors in Python (getters and setters)
mystilleef wrote:
Hello,
Thanks for the responses. The reason I want to change the name of the
attribute is because it doesn't reflect the purpose of the attribute,
anymore. The attribute was originally a string object, but not anymore.
It is primarily a readability issue. There are also a few key
attributes I don't want developers, including myself, fiddling with.
Properties /accessors are good because they allow you to encapsulate
attributes so you can change implementations at will. Some of you have
argued I would have needed to change accessor names too if I had
misnamed them earlier. It's hard to say. I find myself changing the
names of attributes a lot more frequently than I do functions or
methods. Choosing a crappy attribute name is effortless for me,
especially during intense coding sessions. I usually realize I've
choosing a crappy attribute name the next day, sometimes even later.
However, I put a lot more effort into choosing method and function
names, especially when I know it may likely be a public API.
What you need to understand here is that in Python,
1/ methods *are* attributes
2/ every attribute whose name is not prefixed by a leading underscore is
considered part of the api ('__magic__' names being a special case).
So it has nothing to do with data vs method dichotomy (which makes no
sens in a languages where functions and methods are objects), only with
API vs implementation. You choosed a crappy name for an attribute
that's part of the API, so it's *exactly* the same case as if you had
chosen a crappy name for a public method in Java. Think of public data
attributes as magical getter/setters with the most straightforward
behaviour, and of properties as the way to override this default behaviour.
Plus it's
really hard to choose crappy accessor name.
What about getMyCrappyAttributeName/setMyCrappyAttributeName ?-)
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
http://mail.python.org/mailman/listinfo/python-list
Best command for running shell command
I'm a little bit confused about what is the best way to run a shell command, if I want to run a command like xx -a -b yy where I'm not interested in the output, I only want to make sure that the command was executed OK. How should I invoke this (in a Unix/linux environment)? The command module seem to give the resulting output and the various popen commands seem to be similar. -- http://mail.python.org/mailman/listinfo/python-list
Relying on the behaviour of empty container in conditional statements
Hi, my collegues and I recently held a coding style review. All of the code we produced is used in house on a commerical project. One of the minor issues I raised was the common idiom of specifing: pre if len(x) 0: do_something() /pre Instead of using the language-defined bahviour, as stated by PEP8: pre - For sequences, (strings, lists, tuples), use the fact that empty sequences are false. Yes: if not seq: if seq: No: if len(seq) if not len(seq) /pre Without wishing to start a flame war, what are other's opinions on this, is using len safer? If so why? Arguments that have been presented for using codelen(x) 0/code to test emptiness of a container include: - It's safer - Not relying on weird behaviour of the language - Explicit is better than implicit (as stated by 'this' module, Zen of Python) My own feeling is that I am willing to work with the behaviours defined by Python, and treat the use of len in these cases as excessive duplication (this is however, quite a minor point i agree). Note that I have much more experience with the language (6-7 years), whilst the majority of my collegues have about 1-2 years experience. -- http://mail.python.org/mailman/listinfo/python-list
CPU or MB Serial number
Hi, How can I get CPU Serial number , or motherboard serial number with python . I need an idetification of a computer ThanX --- iranian python community -- www.python.ir -- http://mail.python.org/mailman/listinfo/python-list
Re: Best command for running shell command
In article [EMAIL PROTECTED], Donald Duck [EMAIL PROTECTED] wrote: I'm a little bit confused about what is the best way to run a shell command, if I want to run a command like xx -a -b yy where I'm not interested in the output, I only want to make sure that the command was executed OK. How should I invoke this (in a Unix/linux environment)? The most straight-forward way would be: import os status = os.system (xx -a -b yy) if status == 0: print it worked else: print it failed You might also want to look at the new (in 2.4) subprocess module. -- http://mail.python.org/mailman/listinfo/python-list
Re: Relying on the behaviour of empty container in conditional statements
horizon5 wrote:
Hi,
my collegues and I recently held a coding style review.
All of the code we produced is used in house on a commerical project.
One of the minor issues I raised was the common idiom of specifing:
pre
if len(x) 0:
do_something()
/pre
Instead of using the language-defined bahviour, as stated by PEP8:
pre
- For sequences, (strings, lists, tuples), use the fact that empty
sequences are false.
Yes: if not seq:
if seq:
No: if len(seq)
if not len(seq)
/pre
Without wishing to start a flame war, what are other's opinions on
this, is using len safer? If so why?
I fail to see why it would be safer. But I clearly see a drawback to
explicitely testing length of objects : it doesn't work on unsized
objects (like None or 0 or False etc), so it makes code less generic
(wether this is a problem or not in a given context depends of course on
the context).
Arguments that have been presented for using codelen(x) 0/code to
test emptiness of a container include:
- It's safer
cf above
- Not relying on weird behaviour of the language
It's not a weird behaviour, it's a well defined and documented
behaviour. And it's not specific to Python.
- Explicit is better than implicit (as stated by 'this' module, Zen
of Python)
Given that this behaviour is well defined and documented, using if
[not] seq is perfectly explicit.
My own feeling is that I am willing to work with the behaviours defined
by Python,
and use the common Python idiom.
and treat the use of len in these cases as excessive
duplication (this is however, quite a minor point i agree).
It's also not idiomatic and less generic.
Note that I have much more experience with the language (6-7 years),
whilst the majority of my collegues have about 1-2 years experience.
Do they still write code like the following ?
if someBooleanExpression == True:
return True
else:
return False
If yes, time to look for another place to work IMHO. Else, what do they
think of the above snippet, vs:
return someBooleanExpression
Do they think the first one is safer and/or more explicit ?-)
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
http://mail.python.org/mailman/listinfo/python-list
Re: Relying on the behaviour of empty container in conditional statements
On Tue, 11 Jul 2006 04:52:42 -0700, horizon5 wrote: Hi, my collegues and I recently held a coding style review. All of the code we produced is used in house on a commerical project. One of the minor issues I raised was the common idiom of specifing: pre if len(x) 0: do_something() /pre Instead of using the language-defined bahviour, as stated by PEP8: pre - For sequences, (strings, lists, tuples), use the fact that empty sequences are false. Yes: if not seq: if seq: No: if len(seq) if not len(seq) /pre Without wishing to start a flame war, what are other's opinions on this, is using len safer? If so why? What do you mean by safer? What sort of bad consequences are you trying to avoid? What sort of errors do your colleagues think writing if seq encourages? Just waving hands in the air and saying Doing foo is safer is meaningless. Safer than what? What are the costs and benefits of doing foo? What are the consequences of failure? Arguments that have been presented for using codelen(x) 0/code to test emptiness of a container include: - It's safer On the contrary, the longer test isn't safer, it is more dangerous because there is a whole family of potential bugs that can occur when using that idiom, but which can't occur in the shorter test. For example, there are typos like writing len(x) 0 by mistake. (Or, for that matter, len(x) 9.) Do you have a function ln defined in the current scope? Then you better hope that you don't mistype len(x) as ln(x). Sure, the chances of these sorts of errors are small -- but not zero. Write enough tests, and you will surely make them. But they are impossible to make in the shorter if x idiom. - Not relying on weird behaviour of the language There is nothing weird about it. Languages which don't accept arbitrary objects as truth values are weird. Every object should know whether or not it is nonempty/true or empty/false. - Explicit is better than implicit (as stated by 'this' module, Zen of Python) if x: is explicit. It is explicitly asking, does x evaluate as true in a Boolean context or as false? In an object-oriented framework, it is bad practice for the developer to concern himself with what makes an object true or false. Instead, you should simply ask the object, are you true? What happens when you decide that using a list (or tuple) for x is not the right way to solve your problem? You change it to something like, say, a binary tree. Now len(x) 0 is undefined, because trees don't have a length. You could ask if height(x) 0 but calculating the height of a tree is, in general, expensive. Better to simply ask the tree if it is true or false. Or, you subclass list to use a sentinel value. There may be some good reason for not wanting to redefine the __len__ method of the subclass, so the length of the subclassed list is ALWAYS positive, never zero. If you have peppered your code with tests like if len(x) 0, you're in trouble. You're in even greater trouble if some of those tests might be called by *either* regular lists or by the new subclass. Now you have to start turning your tests into something awful like this: if (x.__class__ == ListWithSentinal and len(x) 1) or len(x) 0: But if the subclass redefines the __nonzero__ method, and you use if x as your test, you're done. One change, in one place, compared to potentially hundreds of changes scattered all over your code. There are times where your code is constrained by your data-type, e.g. tests like if len(x) 5: or similar. But they are comparatively rare. Why force simple true/false tests into that idiom? My own feeling is that I am willing to work with the behaviours defined by Python, and treat the use of len in these cases as excessive duplication (this is however, quite a minor point i agree). Note that I have much more experience with the language (6-7 years), whilst the majority of my collegues have about 1-2 years experience. Sounds like they are still programming C or Java in Python. Good luck teaching these young whipper-snappers. *wink* -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
error occurs when using wmi module in child thread
--sample code begin- import threading import wmi def run(*args): c = wmi.WMI () memory=c.Win32_LogicalMemoryConfiguration()[0] info='Total Virtual Memory: '\ +str(int(memory.TotalVirtualMemory)/1024)\ +'MB' print info print Begin run() in main thread run() print Begin run() in child thread thread=threading.Thread(target=run) thread.start() --sample code end--- --debug info begin-- Begin run() in main thread Total Virtual Memory: 1375MB Begin run() in child thread Exception in thread Thread-1: Traceback (most recent call last): File C:\my\Python24\lib\threading.py, line 444, in __bootstrap self.run() File C:\my\Python24\lib\threading.py, line 424, in run self.__target(*self.__args, **self.__kwargs) File F:\chen\code\SoftRepairer\script\test\test.py, line 6, in run c = wmi.WMI () File C:\my\Python24\Lib\site-packages\wmi.py, line 971, in connect handle_com_error (error_info) File C:\my\Python24\Lib\site-packages\wmi.py, line 219, in handle_com_error raise x_wmi, \n.join (exception_string) x_wmi: -0x7ffbfe1c - Invalid syntax --debug info end --info I have found- exception raised at: file: Python24\Lib\site-packages\win32com\client\__init__.py line: 88 code: moniker, i, bindCtx = pythoncom.MkParseDisplayName(Pathname) context: def Moniker(Pathname, clsctx = pythoncom.CLSCTX_ALL): Python friendly version of GetObject's moniker functionality. moniker, i, bindCtx = pythoncom.MkParseDisplayName(Pathname) dispatch = moniker.BindToObject(bindCtx, None, pythoncom.IID_IDispatch) return __WrapDispatch(dispatch, Pathname, clsctx = clsctx) I have compaired the 'Pathname' parameter between main thread and child thread when running, they are the same. ---end-- How can I solve the problem? Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
googling for python restricted execution might give you some clues. I've already assumed that there is no rexec for me as i am using python 2.4. Yeah its much more difficult that my imagination. Should I go for alternatives like 1. Assume every one who is using this webide, wont corrupt system 2. Use some tricks to encrypt the user path and do lots of replacement on user code and o/p. or something else? Best! iapain -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
iapain wrote: I've already assumed that there is no rexec for me as i am using python 2.4. Yeah its much more difficult that my imagination. Should I go for alternatives like 1. Assume every one who is using this webide, wont corrupt system 2. Use some tricks to encrypt the user path and do lots of replacement on user code and o/p. or something else? unless you're willing to build a restricted runtime that runs on top of the core inter- preter, you should assume that anyone writing a Python script that's executed by your program has access to everything that your Python process has access to... /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Relying on the behaviour of empty container in conditional statements
horizon5 wrote: Hi, my collegues and I recently held a coding style review. All of the code we produced is used in house on a commerical project. One of the minor issues I raised was the common idiom of specifing: pre if len(x) 0: do_something() /pre Instead of using the language-defined bahviour, as stated by PEP8: [...] Without wishing to start a flame war, what are other's opinions on this, is using len safer? If so why? All objects evaluate to a boolean, but not all objects support len. So if someone passes x = iter ([]) to your method, then len (x) will result in an exception, whereas 'if x:' will happily (and wrongly) answer true. On the other hand, maybe you should be able to accept iterators, and then the test would look different anyway. My own feeling is that I am willing to work with the behaviours defined by Python, and treat the use of len in these cases as excessive duplication (this is however, quite a minor point i agree). I find if parameters: perfectly acceptable, as it allows parameters to be None as well. On the other hand, I can't stand interpreting integers as booleans, so I wouldn't write if count: Everyone has their personal quirks. Note that I have much more experience with the language (6-7 years), whilst the majority of my collegues have about 1-2 years experience. I guess they're coming from Java and not from Perl :-) Daniel -- http://mail.python.org/mailman/listinfo/python-list
Re: error occurs when using wmi module in child thread
Chen Houwu wrote: --sample code begin- import threading import wmi def run(*args): c = wmi.WMI () memory=c.Win32_LogicalMemoryConfiguration()[0] info='Total Virtual Memory: '\ +str(int(memory.TotalVirtualMemory)/1024)\ +'MB' print info print Begin run() in main thread run() print Begin run() in child thread thread=threading.Thread(target=run) thread.start() I had the same problem and wmi module author (Tim Golden) gave me the solution which; import pythoncom # call this function after the run function definition pythoncom.CoInitialize() So your function becomes; def run(*args): pythoncom.CoInitialize() c = wmi.WMI () memory=c.Win32_LogicalMemoryConfiguration()[0] info='Total Virtual Memory: '\ +str(int(memory.TotalVirtualMemory)/1024)\ +'MB' print info -- Cheers -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
unless you're willing to build a restricted runtime that runs on top of the core inter- preter, you should assume that anyone writing a Python script that's executed by your program has access to everything that your Python process has access to... I think using replacements I can ban atleast OS module and about files, either i should ban file open or write my own module something like rexec, truefully i dont know if I can write that one or not. I was thinking that this gonna take few days but looking much more difficult. Thanks Fred! for nice tutorials on www. -- http://mail.python.org/mailman/listinfo/python-list
Re: error occurs when using wmi module in child thread
thanks to solve my big problem :-) I will try it later. -- http://mail.python.org/mailman/listinfo/python-list
Re: language design question
isinstance(1, object) True What's 1 . len() ? That's easy! since 1 is actually syntactic sugar for set([set([])]), clearly 1.len() == 1. ;-) v. (actually, make that frozenset([frozenset([])])...) -- http://mail.python.org/mailman/listinfo/python-list
Re: language design question
Fredrik Lundh wrote: Bryan wrote: and how do you make sure that everything subclasses this base class ? in this hypothetical case, i was assuming len() would be put in object and every class subclasses object implicitly or explicitly (ie, new style classes only). if it was done that way, would len(obj) == obj.len() in all cases? why should *everything* be forced to have a length ? /F good point. you're right, everything should not have to be forced to have a length. i thought ruby did something like putting length functionality in their highest level base class. then subclasses would either inherit it or could modify it in their own class. my coworker who knows ruby complains about python's len(obj) too. so i assumed ruby implements this in their equivalent base object class. i just briefly searched the ruby docs, but i can't seem to find it. if it is done this way in ruby, then i wonder what happens what obj.length would return for objects that you would not normally associate as having a length, such as what steve holden mentioned 1.length. bryan -- http://mail.python.org/mailman/listinfo/python-list
Abuse of the object-nature of functions?
Hi all, In a framework I've written to test out website, I use something like the following to add functionality at various points: #--- def do_work(callable, data): assertion = False try: assertion = callable.is_assertion except: pass out = callable(data) if assertion: print Test % (Failed, Suceeded)[out] return out def get_assn(fn): def wrapper(*args, **kw): return fn(*args, **kw) out = wrapper out.is_assertion = True return out def funct(data): return True x = funct y = get_assn(funct) do_work(x, data) do_work(y, data) #--- The idea is that I can mark some functions as being assertions, and use the same function for applying the callable to the data and optionally printing some information. This way I needn't worry whether the callable is a custom object or a simple function. The question is, is this a reasonable thing to do? It works, but is it considered bad practice to add attributes to functions? And are there any dangers? -- http://mail.python.org/mailman/listinfo/python-list
Multi-threaded FTP Question
I'm trying to use ftp in python in a multi-threaded way on a windows box - python version 2.4.3. Problem is that it appears that it's only possible to have five instances/threads at one point in time. Errors look like: File C:\Python24\lib\ftplib.py, line 107, in __init__ self.connect(host) File C:\Python24\lib\ftplib.py, line 132, in connect self.welcome = self.getresp() File C:\Python24\lib\ftplib.py, line 208, in getresp resp = self.getmultiline() File C:\Python24\lib\ftplib.py, line 194, in getmultiline line = self.getline() File C:\Python24\lib\ftplib.py, line 184, in getline if not line: raise EOFError EOFError Is it possible to have more than five simultaneous ftp connections? Thanks. Derek -- http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Ant [EMAIL PROTECTED] wrote: The question is, is this a reasonable thing to do? absolutely. a test framework DSL is a perfectly valid use case for function attributes. It works, but is it considered bad practice to add attributes to functions? nope (at least not in small doses ;-) And are there any dangers? nope. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Best command for running shell command
Yes, I highly recommend the subprocess module. subprocess.call() can do almost anything you want to do, and the options are all pretty intuitive Whenever I need to write quick scripts for myself, it's what I use. THN Roy Smith wrote: In article [EMAIL PROTECTED], Donald Duck [EMAIL PROTECTED] wrote: I'm a little bit confused about what is the best way to run a shell command, if I want to run a command like xx -a -b yy where I'm not interested in the output, I only want to make sure that the command was executed OK. How should I invoke this (in a Unix/linux environment)? The most straight-forward way would be: import os status = os.system (xx -a -b yy) if status == 0: print it worked else: print it failed You might also want to look at the new (in 2.4) subprocess module. -- http://mail.python.org/mailman/listinfo/python-list
Re: Multi-threaded FTP Question
On 11 Jul 2006 06:45:42 -0700, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: I'm trying to use ftp in python in a multi-threaded way on a windowsbox - python version 2.4.3.Problem is that it appears that it's onlypossible to have five instances/threads at one point in time.Errorslook like: File C:\Python24\lib\ftplib.py, line 107, in __init__self.connect (host)File C:\Python24\lib\ftplib.py, line 132, in connectself.welcome = self.getresp()File C:\Python24\lib\ftplib.py, line 208, in getrespresp = self.getmultiline() File C:\Python24\lib\ftplib.py, line 194, in getmultilineline = self.getline()File C:\Python24\lib\ftplib.py, line 184, in getlineif not line: raise EOFErrorEOFError Is it possible to have more than five simultaneous ftp connections?Would you mind posting your code? Are you trying to pass the same FTP connection object to all 5 threads? -- Jeremy M. Joneshttp://jeremymjones.com -- http://mail.python.org/mailman/listinfo/python-list
pyExcelerator - Can I read and modify an existing Excel-WorkBook?
Hi I would like to 1. import an existing Excel-sheet (a template) 2. and add some data to it 3. and save it under a different name afterwards. To me it seems, that pyExcelerator does not support the reading for modification of an Excel-sheet. It allows only the parse_xls but I would like to keep the formatting in the template. Did I miss a load, read or open function in pyExcelerator that would hand me back a WorkBook? Greetings, Marco -- http://mail.python.org/mailman/listinfo/python-list
Re: free python hosting !
Luis M. González wrote: I'm curious, why it didn't work? I sent them an email recently, asking about mod_python support, and they replied afirmatively, and very quickly. They also said that they can install other scripts on demand. But I never tried them though... I'd like to know more about your experience with this hosting, if possible. Their support was always great, and they tried several things to get it to work, but I soon got the feeling that although they support mod_python, they didn't really have it set up correctly. They tried different variations of setting up the proper handlers, but nothing ever worked for me, whereas other places I've tried with mod_python, it simply works when you go to a .psp page, for example. Perhaps by now they've fixed it. It is certainly cheap enough to give a shot, and they allow you a few months in which you can cancel and get a refund. -- http://mail.python.org/mailman/listinfo/python-list
Re: Relying on the behaviour of empty container in conditional statements
Le mardi 11 juillet 2006 13:52, horizon5 a écrit : Arguments that have been presented for using codelen(x) 0/code to test emptiness of a container include: - It's safer - Not relying on weird behaviour of the language - Explicit is better than implicit (as stated by 'this' module, Zen of Python) Too bad. From the doc : __nonzero__( self) Called to implement truth value testing, and the built-in operation bool(); should return False or True, or their integer equivalents 0 or 1. When this method is not defined, __len__() is called, if it is defined (see below). If a class defines neither __len__() nor __nonzero__(), all its instances are considered true. So, the bool(container) *is* the test for emptiness for all container in python. What is weird is to not follow the semantic of the language. 'if len(container) : means if container's length is not zero, while if container : means if container is empty. Using the second is far better because a random container can implement a faster algorithm to test its emptiness (the __nonzero__ method for any container in python). -- _ Maric Michaud _ Aristote - www.aristote.info 3 place des tapis 69004 Lyon Tel: +33 426 880 097 -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
On Tue, 11 Jul 2006 06:21:39 -0700, iapain wrote:
unless you're willing to build a restricted runtime that runs on top of the
core inter-
preter, you should assume that anyone writing a Python script that's
executed by
your program has access to everything that your Python process has access
to...
I think using replacements I can ban atleast OS module and about files,
How are you planning on banning the module? Are you thinking about using
source code scanning to detect risky code?
What about modules which export os? It's one thing to ban os, but
did you remember to ban glob.os? How about site.os? And netrc.os? And and
and and...
What about this line of code?
my_innocent_object = __import__(''.join([chr(110+x) for x in [1, 5]]))
Creating a restricted execution environment is *hard*. As far as I know,
even Microsoft has never attempted it. And for all of Sun's resources and
talent, security holes are sometimes found even in Java.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Sybren Stuvel wrote: Ant enlightened us with: try: assertion = callable.is_assertion except: pass Try to make a habit out of catching only the exceptions you know will be thrown. Catching everything generally is a bad idea. In this case, my bet is that catching AttributeError is enough. and assertion = hasattr(callable, is_assertion) is even nicer (and can be done as part of the if-statement after the call, in- stead of in a separate try/except before the call) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: pyExcelerator - Can I read and modify an existing Excel-WorkBook?
Marco Aschwanden wrote: Hi I would like to 1. import an existing Excel-sheet (a template) 2. and add some data to it 3. and save it under a different name afterwards. To me it seems, that pyExcelerator does not support the reading for modification of an Excel-sheet. It allows only the parse_xls but I would like to keep the formatting in the template. Did I miss a load, read or open function in pyExcelerator that would hand me back a WorkBook? Greetings, Marco If you are on Windows, you may find using COM interface to actual Excel application easier. -Larry Bates -- http://mail.python.org/mailman/listinfo/python-list
Re: CPU or MB Serial number
Bayazee wrote:
Hi,
How can I get CPU Serial number , or motherboard serial number with
python . I need an idetification of a computer
ThanX
---
iranian python community -- www.python.ir
If you are on a windows box with WMI (2000 or above) you can use
Python, win32com extentions to get it. The WMI stuff is easily
accessible with Tim Goldens wrapper
http://tgolden.sc.sabren.com/python/wmi.html
import wmi
c = wmi.WMI()
for s in c.Win32_Processor():
... print s
...
instance of Win32_Processor
{
AddressWidth = 32;
Architecture = 0;
Availability = 3;
Caption = x86 Family 15 Model 2 Stepping 4;
CpuStatus = 1;
CreationClassName = Win32_Processor;
CurrentClockSpeed = 1794;
CurrentVoltage = 15;
DataWidth = 32;
Description = x86 Family 15 Model 2 Stepping 4;
DeviceID = CPU0;
ExtClock = 100;
Family = 2;
L2CacheSize = 0;
Level = 15;
LoadPercentage = 7;
Manufacturer = GenuineIntel;
MaxClockSpeed = 1794;
Name = Intel(R) Pentium(R) 4 CPU 1.80GHz;
PowerManagementSupported = FALSE;
ProcessorId = 3FEBFBFF0F24;
ProcessorType = 3;
Revision = 516;
Role = CPU;
SocketDesignation = Microprocessor;
Status = OK;
StatusInfo = 3;
Stepping = 4;
SystemCreationClassName = Win32_ComputerSystem;
SystemName = LON42;
UpgradeMethod = 4;
Version = Model 2, Stepping 4;
};
--
http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
my_innocent_object = __import__(''.join([chr(110+x) for x in [1, 5]]))
Thats really smart way, yeah i had plan to scan and detect but I think
its not gonna work.
Creating a restricted execution environment is *hard*. As far as I know,
even Microsoft has never attempted it. And for all of Sun's resources and
talent, security holes are sometimes found even in Java.
Does that mean there is no way to implement restricted enviorment?
Best!
iapain
--
http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Chris Smith wrote: David Hopwood [EMAIL PROTECTED] wrote: Maybe I'm not understanding what you mean by complete. Of course any type system of this expressive power will be incomplete (whether or not it can express conditions 3 to 5), in the sense that it cannot prove all true assertions about the types of expressions. Ah. I meant complete enough to accomplish the goal in this subthread, which was to ensure that the compiler knows when a particular int variable is guaranteed to be greater than 18, and when it is not. I don't think that placing too much emphasis on any individual example is the right way of thinking about this. What matters is that, over the range of typical programs written in the language, the value of the increased confidence in program correctness outweighs the effort involved in both adding annotations, and understanding whether any remaining run-time checks are guaranteed to succeed. Look at it this way: suppose that I *need* to verify that a program has no range errors. Doing that entirely manually would be extremely tedious. If the compiler can do, say, 90% of the work, and point out the places that need to be verified manually, then that would be both less tedious, and less error-prone. -- David Hopwood [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Identifying apparently unused globals
At work we have a fairly large application (about 20 packages, 300+ modules) that looks like we might be heading into a bit of a plateau stage. Now seems like a good time to identify and delete old, unused code that's flown under the radar screen for awhile simply because nobody was looking for it. Trouble is, most of that unused code consists of module-level classes, functions and variables, so it's hard to distinguish mechanically from code that *is* used. Is there a tool out there that will slurp in a number of packages, identify all the global names then remove those that it determines are referenced? (Yes, I know it's impossible to do this in general. We have one very restricted exec statement and no eval() calls, so I'm not too worried about that sort of obfuscation.) Thx, Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: Best command for running shell command
where I'm not interested in the output, I only want to make sure that the command was executed OK. How should I invoke this (in a Unix/linux environment)? Remember few things about executing program within python 1. Create a subprocess or child process and execute it. 2. You should use Timeout stratagy i.e your execution took more than provided time then timeout this process. In linux/unix you may use singnal alarm to implement it. Best! -- http://mail.python.org/mailman/listinfo/python-list
os.access() problem
I just got a new PC with Windows XP, and I want to run Leo on it. Leo uses the os.access() function to check for read-only files. For some reason, os.access(filename, os.W_OK) always returns false. I wrote a 2-liner Python script to just test os.access on any file. I have tried this with Python 2.4 and 2.5b1. I have uninstalled and re-installed Python and Leo. I have fiddled with file permissions on the target files as well as on the Python installation itself. I have used cacls to check the access control lists (and although I'm not exactly certain what to do with this information, it appears to be ok - I think). None of the above has helped me to identify or fix the problem. A scan of the Python newsgroup suggests that os.access() may not be the best way to check for read-only, but the discussion is a bit deeper than my understanding, so I'm not sure there's anything to it in this case. I realize this must be a Windows permissions thing, but I just can't figure it out. I'm no expert in Windows security beyond basic permissions, so I could be missing something simple. Can anyone offer any suggestions? Thanks, Phil -- http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Fredrik Lundh wrote: Sybren Stuvel wrote: Ant enlightened us with: try: assertion = callable.is_assertion except: pass Try to make a habit out of catching only the exceptions you know will be thrown. Catching everything generally is a bad idea. In this case, my bet is that catching AttributeError is enough. and assertion = hasattr(callable, is_assertion) is even nicer (and can be done as part of the if-statement after the call, in- stead of in a separate try/except before the call) You would normally expect that you can turn off a flag by setting it to False instead of deleting it -- which is also how the OP's code works. So I would prefer assertion = getattr(callable, is_assertion, False) if you forgo the explicit try...except. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
iapain wrote:
my_innocent_object = __import__(''.join([chr(110+x) for x in [1, 5]]))
Thats really smart way, yeah i had plan to scan and detect but I think
its not gonna work.
Creating a restricted execution environment is *hard*. As far as I know,
even Microsoft has never attempted it. And for all of Sun's resources and
talent, security holes are sometimes found even in Java.
Does that mean there is no way to implement restricted enviorment?
In a nutshell: yes, especially if not designed from ground up that way. If
you need it, the best thing to do is to put some distance between your code
and the possibly malicious one, using some RPC.
Diez
--
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timeit module for comparing the performance of two scripts
Hi,
Following are my files.
In the format:
Filename
content
config1.txt
#DataBase Repository file
dbRepository = omsa_disney.xml
config2.txt
# Configfile for sendmail
[Sendmail]
userprefix = testuser
pyConfig.py
import re
def pyConfig():
fhandle = open( 'config1.txt', 'r' )
arr = fhandle.readlines()
fhandle.close()
hash = {}
for item in arr:
txt = item.strip()
if re.search( '^\s*$', txt ):
continue
if re.search( '^#.*$', txt ):
continue
if not re.search( '^\s*(\w|\W)+\s*=\s*(\w|\W)+\s*$', txt ):
continue
hash[txt.split( '=' )[0].strip().lower()] = txt.split( '='
)[1].strip()
print hash['dbrepository']
pyConparse.py
from ConfigParser import ConfigParser
def pyConParse():
configparser = ConfigParser()
configparser.read('config2.txt')
print configparser.get('Sendmail','userprefix')
Question is:
How do I compare the performance of pyConfig.py vs pyConparse.py using
timeit module?
I tried it as the way it is mentioned in the example, but when I do
Timer(pyConfig(),from __main__ import pyConfig), it imports
pyConfig in infinite loop. ( How does the python doc example on timeit
work? Anyone tried it?)
I just need to compare pyConfig.py and pyParse.py. ( And as general
question x.py and y.py)
How I can do it? Please consider this as a newbie question as well.
Thanks,
Senthil
--
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Re: std in and stdout
Juergen Huber wrote: how would i fix the following problem: now i have an input file with a fix name and an output file! i have this two files hardcoded written in the sourcecode of this function! in the future i will start this script with the command line. the syntax should be look like this: Python Function | Source File| Output File --- fileanalyse.pysourcefile.csv filenalyse.txt i will call the programm always with the commandline, that i could type in various filenames for the input and output files! could anybody help me?! Are you perhaps looking for sys.argv? The following example takes filenames from the command line and defaults to stdin/stdout: import sys def analyse(instream, outstream): pass # your code instream = sys.stdin outstream = sys.stdout if len(sys.argv) 1: instream = open(sys.argv[1]) if len(sys.argv) 2: outstream = open(sys.argv[2], w) analyse(instream, outstream) instream.close() outstream.close() Peter PS: You might be interested in posting to the oh so quiet german-language de.comp.lang.python -- http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Peter Otten wrote: You would normally expect that you can turn off a flag by setting it to False instead of deleting it -- which is also how the OP's code works. So I would prefer assertion = getattr(callable, is_assertion, False) agreed (but note that the OP used a decorator to set the attribute, so you could consider it an implementation detail...) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Augument assignment versus regular assignment
Antoon Pardon [EMAIL PROTECTED] (AP) wrote: AP As I read the language reference the x stands for a target expression. AP Now what does it mean to evaluate a target expression like col[key]. AP IMO it means finding the location of the item in the collection: the AP bucket in the directory, the node in the tree ... grosso mode it AP boils down to the call to __setitem__ or __getitem__ depending AP on where the col[key] was located in the line (or if you prefer AP the view from the interpreter it boils down to the BINARY_SUBSCR AP and STORE_SUBSCR opcodes). AP So if the language reference seems to implies that col[key] will AP only be evaluated once in a line like: col[key] += 1 I expect AP only one call from __setitem__ or __getitem__ (or only one AP from BINARY_SUBSCR or STORE_SUBSCR) You need both the __setitem__ and the __getitem__ otherwise it won't work. I think the evaluated once clause is for cases like: f(a)[g(b)] += 1 where f and/or g have side effects. These side effects should then take place only once. Side effects in __setitem__ and __getitem__ is not what it is talking about. -- Piet van Oostrum [EMAIL PROTECTED] URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4] Private email: [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: threading troubles
sreekant [EMAIL PROTECTED] (S) wrote: S I decided in the end to use fork and all is well. But how are you doing the callback then? From your code it looks like the callback is called after the external command finishes. The callback would then be called in the child process, not in the parent process, I think. Or do you have a solution for that? -- Piet van Oostrum [EMAIL PROTECTED] URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4] Private email: [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: timeit module for comparing the performance of two scripts
Phoe6 [EMAIL PROTECTED] wrote: How do I compare the performance of pyConfig.py vs pyConparse.py using timeit module? $ python -m timeit -s import pyConfig pyConfig.pyConfig() $ python -m timeit -s import pyConparse pyConparse.pyConParse() note that timeit runs the benchmarked function multiple times, so you may want to remove the print statements. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Python in a nutshell - new edition ?
End of July is our aggressive but still-achievable target: everythingwas scheduled from the start to hit OSCON '06 (and the release of Python 2.5 -- whether 2.5 final will be out at OSCON is still uncertain,though).Currently the schedule has Python 2.5 final due August 8th, and RC1 August 1st. That means that we'll be out just after OSCON. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
David Hopwood [EMAIL PROTECTED] wrote: I don't think that placing too much emphasis on any individual example is the right way of thinking about this. What matters is that, over the range of typical programs written in the language, the value of the increased confidence in program correctness outweighs the effort involved in both adding annotations, and understanding whether any remaining run-time checks are guaranteed to succeed. Are you really that short on people to disagree with? In this particular branch of this thread, we were discussing George's objection that it would be ridiculous for a type system to check that a variable should be greater than 18. There is no such thing as placing too much emphasis on what we were actually discussing. If you want to discuss something else, feel free to post about it. Why does it bother you that I'm considering George's point? -- Chris Smith - Lead Software Developer / Technical Trainer MindIQ Corporation -- http://mail.python.org/mailman/listinfo/python-list
Re: timeit module for comparing the performance of two scripts
Fredrik Lundh wrote: $ python -m timeit -s import pyConfig pyConfig.pyConfig() $ python -m timeit -s import pyConparse pyConparse.pyConParse() note that timeit runs the benchmarked function multiple times, so you may want to remove the print statements. Thanks a lot Fredrik!. I did not know that timeit runs benchmarked function multiple times. I got scared with multiple prints and thought import pyConfig has put it in infinite loop and I had killed the program. I could use Timer function as well. Thanks, Senthil -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Marcin 'Qrczak' Kowalczyk [EMAIL PROTECTED] wrote:
Chris Smith [EMAIL PROTECTED] writes:
No what happens if right here you code
b := 16;
Does that again change the type of b? Or is that an illegal
instruction, because b has the local type of (18..22)?
It arranges that the expression b after that line (barring further
changes) has type int{16..16}, which would make the later call to
signContract illegal.
The assignment might be performed in a function called there, so it's
not visible locally.
Indeed, I pointed that out a few messages ago. That doesn't mean it's
impossible, but it does mean that it's more difficult. Eventually, the
compiler will have to stop checking something, somewhere. It certainly
doesn't, though, have to stop at the first functional abstraction it
comes to. The ways that a function modifies the global application
state certainly ought to be considered part of the visible API of that
function, and if we could reasonably express that in a type system, then
that's great! Granted, designing such a type system for an arbitrary
imperative language seems a little scary.
Propagating constraints from conditionals is not applicable to mutable
variables, at least not easily.
Certainly it worked in the code from my original response to George.
Regardless of whether it might not work in more complex scenarios (and I
think it could, though it would be more challenging), it still doesn't
seem reasonable to assert that the technique is not applicable. If the
type system fails, then it fails conservatively as always, and some
programmer annotation and runtime check is needed to enforce the
condition.
I think that constant bounds are not very useful at all. Most ranges
are not known statically, e.g. a variable can span the size of an
array.
I think you are overestimating the difficulties here. Specialized
language already exist that reliably (as in, all the time) move array
bounds checking to compile time; that means that there exist at least
some languages that have already solved this problem. Going back to my
handy copy of Pierce's book again, he claims that range checking is a
solved problem in theory, and the only remaining work is in how to
integrate it into a program without prohibitive amounts of type
annotation.
--
Chris Smith - Lead Software Developer / Technical Trainer
MindIQ Corporation
--
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Subject: RELEASED Python 2.5 (beta 2)
On behalf of the Python development team and the Python community, I'm happy to announce the second BETA release of Python 2.5. This is an *beta* release of Python 2.5. As such, it is not suitable for a production environment. It is being released to solicit feedback and hopefully discover bugs, as well as allowing you to determine how changes in 2.5 might impact you. If you find things broken or incorrect, please log a bug on Sourceforge. In particular, note that changes to improve Python's support of 64 bit systems might require authors of C extensions to change their code. More information (as well as source distributions and Windows installers) are available from the 2.5 website: http://www.python.org/2.5/ A Universal Mac OSX Installer will be available shortly - in the meantime, Mac users can build from the source tarballs. Since the first beta, a large number of bug fixes have been made to Python 2.5 - see the release notes (available from the 2.5 webpage) for the full details. There has been one very small new feature added - the sys._current_frames() function was added. This is extremely useful for tracking down deadlocks and related problems - a similar technique is already used in the popular DeadlockDebugger extension for Zope. It is not possible to do this sort of debugging from outside the Python core safely and robustly, which is why we've snuck this in after the feature freeze. As of this release, Python 2.5 is now in *feature freeze*. Unless absolutely necessary, no functionality changes will be made between now and the final release of Python 2.5. The plan is for this to be the final beta release. We should now move to one or more release candidates, leading to a 2.5 final release early August. PEP 356 includes the schedule and will be updated as the schedule evolves. At this point, any testing you can do would be greatly, greatly appreciated. The new features in Python 2.5 are described in Andrew Kuchling's What's New In Python 2.5. It's available from the 2.5 web page. Amongst the language features added include conditional expressions, the with statement, the merge of try/except and try/finally into try/except/finally, enhancements to generators to produce a coroutine kind of functionality, and a brand new AST-based compiler implementation. New modules added include hashlib, ElementTree, sqlite3, wsgiref and ctypes. In addition, a new profiling module cProfile was added. Enjoy this new release, Anthony Anthony Baxter [EMAIL PROTECTED] Python Release Manager (on behalf of the entire python-dev team) pgpefHF3jJ6yF.pgp Description: PGP signature -- http://mail.python.org/mailman/listinfo/python-list
Re: pyExcelerator - Can I read and modify an existing Excel-WorkBook?
I'm pretty sure it doesn't support reading an existing document. That would be useful. On 7/11/06, Larry Bates [EMAIL PROTECTED] wrote: Marco Aschwanden wrote: Hi I would like to 1. import an existing Excel-sheet (a template) 2. and add some data to it 3. and save it under a different name afterwards. To me it seems, that pyExcelerator does not support the reading for modification of an Excel-sheet. It allows only the parse_xls but I would like to keep the formatting in the template. Did I miss a load, read or open function in pyExcelerator that would hand me back a WorkBook? Greetings, Marco If you are on Windows, you may find using COM interface to actual Excel application easier. -Larry Bates -- http://mail.python.org/mailman/listinfo/python-list -- Gregory Piñero Chief Innovation Officer Blended Technologies (www.blendedtechnologies.com) -- http://mail.python.org/mailman/listinfo/python-list
Re: timeit module for comparing the performance of two scripts
Phoe6 $ python -m timeit -s import pyConfig pyConfig.pyConfig() $ python -m timeit -s import pyConparse pyConparse.pyConParse() note that timeit runs the benchmarked function multiple times, so you may want to remove the print statements. Thanks a lot Fredrik!. I did not know that timeit runs benchmarked function multiple times. I got scared with multiple prints and thought import pyConfig has put it in infinite loop and I had killed the program. I could use Timer function as well. for cases like this, the command form gives a better result with less effort; it picks a suitable number of iterations based on how fast the code actually runs, instead of using a fixed number, and it also runs the test multiple times, and picks the smallest observed time. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: syslog best practices -- when to call closelog?
In article [EMAIL PROTECTED], J Rice [EMAIL PROTECTED] wrote: I have a question: When should syslog.closelog() be called? I have a daemon that spends most of its time asleep and quiet, but writes messages to the mail log when active. Should I open the log at the start and keep it open until the program closes? This seems much simpler than issuing three commands everytime I want to write to the log. The program will essentially be running constantly. Is having the log constantly open a problem? What happens if the program crashes or is killed without a closelog()? Jeff In your terms, it's entirely safe to leave open the handle to syslog. The operating system takes responsibility for cleanup on shutdown of your application. -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
In article [EMAIL PROTECTED], iapain [EMAIL PROTECTED] wrote: . . . Does that mean there is no way to implement restricted enviorment? . . . The most knowledgeable people have effectively given up, in regard to Python. As it happens, though, Tcl *does* admit quite an interesting restricted-execution model. Tcl was widely used in the '90s for agent experiments, and its safe interpreters are arguably more reliable than Java's restricted environment. Tcl is also roughly comparable to Python in its power and convenience for the individual developer. Should you want to pursue this subject, URL: http://wiki.tcl.tk/safe and URL: http://wiki.tcl.tk/interp might interest you. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Marshall wrote: Now, I'm not fully up to speed on DBC. The contract specifications, these are specified statically, but checked dynamically, is that right? Yes, but there's a bunch more to it than that. The handling of exceptions, an in particular exceptions caused by failed pre/post conditions, is an integral part of the process. Plus, of course, pre/post condition checking is turned off while checking pre/post conditions. This does make sense if you think about it long enough, but it took me several months before I realized why it's necessary theoretically rather than just practically. Wouldn't it be possible to do them at compile time? For some particularly simple ones, yes. For others, like the chess pieces are in a position it is legal to get to from a standard opening set-up, it would be difficult. Anything to do with I/O is going to be almost impossible to write a checkable postcondition for, even at runtime. After this call, the reader at the other end of the socket will receive the bytes in argument 2 without change. As far as I understand it, Eiffel compilers don't even make use of postconditions to optimize code or eliminate run-time checks (like null pointer testing). -- Darren New / San Diego, CA, USA (PST) This octopus isn't tasty. Too many tentacles, not enough chops. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Marcin 'Qrczak' Kowalczyk wrote: The assignment might be performed in a function called there, so it's not visible locally. In Hermes, which actually does this sort of constraint propagation, you don't have the ability[1] to munge some other routine's[2] local variables, so that becomes a non-issue. You wind up with some strange constructs, tho, like an assignment statement that copies and a different assignment statement that puts the rvalue into the variable on the left while simultaneously destroying whatever variable held the rvalue. [1] You do. Just not in a way visible to the programmer. The compiler manages to optimize out most places that different names consistantly refer to the same value. [2] There aren't subroutines. Just processes, with their own address space, to which you send and receive messages. -- Darren New / San Diego, CA, USA (PST) This octopus isn't tasty. Too many tentacles, not enough chops. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Chris Smith wrote: Specialized language already exist that reliably (as in, all the time) move array bounds checking to compile time; It sounds like this means the programmer has to code up what it means to index off an array, yes? Otherwise, I can't imagine how it would work. x := read_integer_from_stdin(); write_to_stdout(myarray[x]); What does the programmer have to do to implement this semantic in the sort of language you're talking about? Surely something somewhere along the line has to fail (for some meaning of failure) at run-time, yes? -- Darren New / San Diego, CA, USA (PST) This octopus isn't tasty. Too many tentacles, not enough chops. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Chris Smith wrote: Going back to my handy copy of Pierce's book again, he claims that range checking is a solved problem in theory, and the only remaining work is in how to integrate it into a program without prohibitive amounts of type annotation. This is in TAPL? Or ATTPL? Can you cite it a bit more specifically? I want to reread that. Marshall -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
Steven D'Aprano wrote: Creating a restricted execution environment is *hard*. As far as I know, even Microsoft has never attempted it. And for all of Sun's resources and talent, security holes are sometimes found even in Java. Java is not the only restricted execution environment around. Javascript, as implemented by most browsers, is an excellent lightweight restricted execution environment, and there are many browsers which have good implementations. Regards Sreeram signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
win32 and System Font Size
Hello all, I'm writing a windows application with a Tkinter GUI. Tkinter ignores the Windows user setting for system default font size - which can be 'normal', 'large' or 'extra large'. Does anyone know how to retrieve this information from the win32api, or using win32com ? All the best, Fuzzyman http://www.voidspace.org.uk/python/index.shtml -- http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Sybren wrote: Try to make a habit out of catching only the exceptions you know will be thrown. Yes - you are right of course - this was just a minimal example of course to illustrate the sort of thing I'm using function attriutes for. Fredrik Lundh wrote: Peter Otten wrote: assertion = getattr(callable, is_assertion, False) I like this way of doing it, as it is possible I may have a function that could feasibly be either an assertion or otherwise depending on context. agreed (but note that the OP used a decorator to set the attribute, so you could consider it an implementation detail...) The main reason for using a decorator was to avoid problems like the following whilst providing an easy way of adding the attribute: def assn_or_other(data): ... return False ... # I want x to be treated as normal. ... x = assn_or_other # I want y to be an assertion ... y = assn_or_other y.is_assertion = True x.is_assertion True -- http://mail.python.org/mailman/listinfo/python-list
Re: Identifying apparently unused globals
[EMAIL PROTECTED] wrote: At work we have a fairly large application (about 20 packages, 300+ modules) that looks like we might be heading into a bit of a plateau stage. Now seems like a good time to identify and delete old, unused code that's flown under the radar screen for awhile simply because nobody was looking for it. Trouble is, most of that unused code consists of module-level classes, functions and variables, so it's hard to distinguish mechanically from code that *is* used. Is there a tool out there that will slurp in a number of packages, identify all the global names then remove those that it determines are referenced? (Yes, I know it's impossible to do this in general. We have one very restricted exec statement and no eval() calls, so I'm not too worried about that sort of obfuscation.) Thx, Skip I haven't used it myself, but pychecker (http://pychecker.sourceforge.net/) is supposed to be able to perform such stunts. From the page: Types of problems that can be found include: Unused globals and locals (module or variable) HTH, ~Simon -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
The most knowledgeable people have effectively given up, in regard to Python. I guess now I am up with only one option, i.e hope that user input code wont be evil to the system. **which is rarely possible** -- http://mail.python.org/mailman/listinfo/python-list
Re: Abuse of the object-nature of functions?
Sybren Stuvel wrote: Ant enlightened us with: try: assertion = callable.is_assertion except: pass Try to make a habit out of catching only the exceptions you know will be thrown. Catching everything generally is a bad idea. In this case, my bet is that catching AttributeError is enough. What about doing exception kind of like a C switch statement with a default case: try: do_something() except TypeError: fix_something() except: print Unknown error, you are doomed traceback.print_exc() #something to print the traceback exit_gracefully() Is this frowned upon? You still handle the error and you know where it happened and what happened. Anything wrong with this? I don't like the idea of my system crashing for any reason. -carl -- Carl J. Van Arsdall [EMAIL PROTECTED] Build and Release MontaVista Software -- http://mail.python.org/mailman/listinfo/python-list
Re: Restricted Access
K.S.Sreeram [EMAIL PROTECTED] writes: Java is not the only restricted execution environment around. Javascript, as implemented by most browsers, is an excellent lightweight restricted execution environment, and there are many browsers which have good implementations. And we hear about browser security bugs all the time, for which the workaround is shut off javascript. -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
On Tue, 11 Jul 2006 14:59:46 GMT, David Hopwood [EMAIL PROTECTED] wrote: What matters is that, over the range of typical programs written in the language, the value of the increased confidence in program correctness outweighs the effort involved in both adding annotations, and understanding whether any remaining run-time checks are guaranteed to succeed. Agreed, but ... Look at it this way: suppose that I *need* to verify that a program has no range errors. Doing that entirely manually would be extremely tedious. If the compiler can do, say, 90% of the work, and point out the places that need to be verified manually, then that would be both less tedious, and less error-prone. All of this presupposes that you have a high level of confidence in the compiler. I've been in software development for going in 20 years now and worked 10 years on high performance, high availability systems. In all that time I have yet to meet a compiler ... or significant program of any kind ... that is without bugs, noticeable or not. I'm a fan of static typing but the major problem I have with complex inferencing (in general) is the black box aspect of it. That is, when the compiler rejects my code, is it really because a) I was stupid, b) the types are too complex, or c) the compiler itself has a bug. It's certainly true that the vast majority of my problems are because I'm stupid, but I've run into actual compiler bugs far too often for my liking (high performance coding has a tendency to uncover them). I think I understand how to implement HM inferencing ... I haven't actually done it yet, but I've studied it and I'm working on a toy language that will eventually use it. But HM itself is a toy compared to an inferencing system that could realistically handle some of the problems that were discussed in this and Xah's expressiveness thread (my own beef is with *static* checking of range narrowing assignments which I still don't believe can be done regardless of Chris Smith's assertions to the contrary). It seems to me that the code complexity of such a super-duper inferencing system would make its bug free implementation quite difficult and I personally would be less inclined to trust a compiler that used it than one having a less capable (but easier to implement) system. George -- for email reply remove / from address -- http://mail.python.org/mailman/listinfo/python-list
Re: What is a type error?
Marshall [EMAIL PROTECTED] wrote: Chris Smith wrote: Going back to my handy copy of Pierce's book again, he claims that range checking is a solved problem in theory, and the only remaining work is in how to integrate it into a program without prohibitive amounts of type annotation. This is in TAPL? Or ATTPL? Can you cite it a bit more specifically? I want to reread that. It's TAPL. On further review, I may have done more interpretation than I remembered. In particular, the discussion is limited to array bounds checking, though I don't see a fundamental reason why it wouldn't extend to other kinds of range checking against constant ranges as we've been discussing here. Relevant sections are: Page 7 footnote: Mentions other challenges such as tractability that seem more fundamental, but those are treated as trading off against complexity of annotations; in other words, if we didn't require so many annotations, then it might become computationally intractable. The next reference better regarding tractability. Section 30.5, pp. 460 - 465: Gives a specific example of a language (theoretical) developed to use limited dependent types to eliminate array bounds checking. There's a specific mention there that it can be made tractable because the specific case of dependent types needed for bounds checking happens to have efficient algorithms, although dependent types are intractable in the general case. I'm afraid that's all I've got. I also have come across a real-life (though not general purpose) languages that does bounds checking elimination via these techniques... but I can't find them now for the life of me. I'll post if I remember what it is, soon. -- Chris Smith - Lead Software Developer / Technical Trainer MindIQ Corporation -- http://mail.python.org/mailman/listinfo/python-list
Re: Identifying apparently unused globals
Simon I haven't used it myself, but pychecker Simon (http://pychecker.sourceforge.net/) is supposed to be able to Simon perform such stunts. From the page: Types of problems that can Simon be found include: Unused globals and locals (module or variable) Thanks. I've used both pylint and pychecker. I'm not aware that either one can do what I want. Here's a trivial example: Module a.py: RED = red BLUE = blue Module b.py: import a print a.RED Considering modules a and b as a whole program, a.BLUE is unused anywhere in the program. Skip -- http://mail.python.org/mailman/listinfo/python-list
