Mailman 3 May 2008 - Python-Dev

A smarter shutil.copytree ?
by Tarek Ziadé May 21, 2008

May 21, 2008

Hi, shutil.copytree is very convenient to make recursive copies, but os.walk has to be used everytime some filtering has to be done on the files copied., if you want to avoid copying some files. The code pattern with os.walk is pretty talkative : --------------------- copying a source folder to a target folder, but the pyc/pyo files os.mkdir(target) for root, dirs, filenames in os.walk(source): root_target = root.replace(source, target) for dir_ in dirs: target_dir = join(… [View More]

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Proposal: new environment variable PYTHONSTDOUTENCODING
by "Martin v. Löwis" May 21, 2008

May 21, 2008

I'd like to propose a new environment variable PYTHONSTDOUTENCODING. This is meant to solve various problems that people had with Python not detecting their terminal encoding correctly; it would override any detection that Python would use for determining the encoding of stdout (and stdin - but that's less relevant in 2.x). In particular, setting this environment variable would also disable the detection of whether stdout is a terminal. This is desirable for cases as the pydev eclipse plugin, … [View More]

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disappearing exceptions
by Benjamin Peterson May 21, 2008

May 21, 2008

In several places in the C code, there are instances where all exceptions can be completely ignored (akin to a bare except statement.) after a PyObject_GetAttr call. A week ago, I fixed one of these in hasattr (issue 2196) by propagating exceptions that don't inherit Exception (SystemExit, KeyboardInterrupt). However, there is another patch that propagates anything that is not a AttributeError (issue 1574217). How should we approach this? -- Cheers, Benjamin Peterson "There's no place like 127.0.0.1."

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Possible bug in re module?
by Dmitry Vasiliev May 20, 2008

May 20, 2008

I've just found a strange re behavior: >>> import re >>> re.sub("(?:ab|b|a)", "+", "cbacbabcabc") 'c++c++c+c' >>> re.sub("(?:ab|b|a){2}", "+", "cbacbabcabc") 'c+c+c+c' In the last case |-separated expressions seems don't tried from left to right. Is it bug or just me? -- Dmitry Vasiliev <dima at hlabs.spb.ru> http://hlabs.spb.ru

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Re: [Python-Dev] Addition of "pyprocessing" module to standard lib.
by Leif Walsh May 20, 2008

May 20, 2008

On Mon, 19 May 2008, Bill Janssen wrote: > > On Mon, May 19, 2008 at 5:15 PM, Bill Janssen <janssen(a)parc.com> wrote: > > >> If you can run a pure Python module > > >> that does not depend on any C extension, then that platform has the > > >> support needed to run Python. > > > > > > This is certainly a point of view. One that many end-users wouldn't > > > understand :-). > > > > Perhaps, but it's clear-cut.… [View More]

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Module renaming and pickle mechanisms
by M.-A. Lemburg May 20, 2008

May 20, 2008

I'd like to bring a potential problem to attention that is caused by the recent module renaming approach: Object serialization protocols like e.g. pickle usually store the complete module path to the object class together with the object. They access this module path by looking at the __module__ attribute of the object classes. With the renaming, all objects which use classes from the renamed modules will now refer to the renamed modules in their serialized form, e.g. queue.Queue instead of … [View More]Queue.Queue (just to name one example). While this is nice for forward compatibility, it causes rather serious problems for making object serialization backwards compatible, since the older Python versions can no longer unserialize objects due to missing modules. This can happen in client-server setups where e.g. the server uses Python 2.6 and the clients some other Python version (e.g. Python 2.5). It can also happen in storage setups where Python objects are stored using e.g. pickle, ZODB being a prominent example. As soon as a Python 2.6 application starts writing to such storages, Python 2.5 and lower versions will no longer be able to read back all the data. Now, I think there's a way to solve this puzzle: Instead of renaming the modules (e.g. Queue -> queue), we leave the code in the existing modules and packages and instead add the new module names and package structure with pointers and redirects to the existing 2.5 modules. Code can (and probably should) still be changed to try to import the new module name. In cases where backwards compatibility is needed, this can also be done using try: import newname except ImportError: import oldname Later on, when porting applications to 3.0, the 2to3 script can then apply the final renaming in the source code. Example: queue.py: --------- import sys, Queue sys.modules[__name__] = Queue -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, May 17 2008) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ :::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,MacOSX for free ! :::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 [View Less]

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Unaccompanied Patch
by Graham Horler May 20, 2008

May 20, 2008

Hi all, I created a patch on 2007-08-15: http://bugs.python.org/issue1775025 I wonder, will it just stay in patches unnoticed until it has its very own associated bug report to keep it company? Thanks, Graham

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Symbolic errno values in error messages
by Yannick Gingras May 19, 2008

May 19, 2008

Hi, I spent some time googleing for "OSError 4" before it occurred to me that "4" was actually an irrelevant implementation detail. As soon as I searched for "EINTR", I found exactly what I was looking for. (not really but this is another story) I jumped to the conclusion that OSError.__str__() should return the symbolic error number instead of the integer value. I was about to write a patch but I just noticed that OSError and friends are implemented in C so I guess it will be a bit … [View More]

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Re: [Python-Dev] Symbolic errno values in error messages
by Yannick Gingras May 19, 2008

May 19, 2008

"Guido van Rossum" <guido(a)python.org> writes: > Have you considered whether this works on all platforms? (E.g. > Windows, or embedded non-Unix-based.) Yes but I guess I didn't comment it properly. The line printed_errno = errno_str ? errno_str : self->myerrno; ensures that we gracefully fallback to numeric errno when here is no symbolic value available. The code is only invoked if there is an errno value, which takes care of most non-Unix platforms. -- Yannick Gingras

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Conditional For Statements
by Ryan Hitchman May 19, 2008

May 19, 2008

I'd like to propose an addition to the for statement's syntax: for {variable} in {iterable} if {condition}: {block} which is equivalent to for {variable} in {iterable}: if not {condition}: continue {block} and for {variable} in filter(lambda: {condition}, iterable): {block} This would make the syntax closer to that of generators, which have 'for variable in iterable if condition', and would improve code clarity by increased brevity and not negating boolean … [View More]

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