Mailman 3 May 2011 - Python-ideas

proposal: module-level __init__
by Daniel Holth May 7, 2011

May 7, 2011

__all__ is very useful when doing import *, which is frowned upon. As an alternative, allow modules to contain a function called __init__ that defines that module's exported symbols by way of the global statement. By importing modules that are used, but not intended to be exported, inside the __init__ function, programmers avoid cases such as the unintentional 'somemodule.sys' (referring to a module by its non-canonical name) that makes it harder to refactor larger projects. Before: __all__ = … [View More]

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AttributeError: __exit__
by Daniel Holth May 7, 2011

May 7, 2011

I just learned about Python internals from The ZODB transaction module. In Python < 2.7, the module works as a transaction manager. More or less: manager = Foo() __exit__ = manager.__exit__ __enter__ = manager.__enter__ After Python 2.7, it doesn't work. import transaction with transaction: pass >>> AttributeError: __exit__ It should be obvious to even the most casual observer that the exception is because, after Python 2.7, the with: statement has its own opcode that bypasses … [View More]

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thoughts on regular expression improvements
by Bill Janssen May 7, 2011

May 7, 2011

I've been doing a lot of RE hacking lately, and some possible improvements suggest themselves. 1. Multiple occurrences of a named group Right now, you can compose RE's with x = re.compile("...") y = re.compile("..." + x.pattern + "...") But if x contains named groups, you run into trouble if you have something like z = re.compile("..." + x.pattern + "..." + x.pattern + "...") which can easily happen if x could occur at various places in z. The issue is that a named group is … [View More]

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Re: [Python-ideas] 1_000_000
by Laura Creighton May 7, 2011

May 7, 2011

If you disallow variable names of the form _<some number> you will break a huge amount of my automatically generated code. Admittedly, it wouldn't be hard to change things so that the generated variables are now X<some number> instead, but that happens to be the way I have written it now. Laura

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Re: [Python-ideas] 1_000_000
by Kirubakaran May 6, 2011

May 6, 2011

Ah, thanks. Sorry, I don't know how I failed to see that. On Fri, May 6, 2011 at 2:30 PM, Andre Roberge <andre.roberge(a)gmail.com>wrote: > I believe that the original suggestion was meant to be more general than > the specific suggestions for powers of 10. For example, consider the > following hypothetical: > > for i in range(1, 1_111_111_111, 1024): > pass > > where the _ really helps in figuring out the size. > > André > > > On Fri, May 6, … [View More]

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Re: [Python-ideas] [Python-Dev] What if replacing items in a dictionary returns the new dictionary?
by Roy Hyunjin Han May 5, 2011

May 5, 2011

2011/5/5 Giuseppe Ottaviano <giuott(a)gmail.com>: >> The only thing I would add is obj.copy(), to ensure that the original >> dictionary is unchanged. >> >> class using(object): >> def __init__(self, obj): >> self._wrappee = obj.copy() > > My example was just a proof of concept, there are many other things > that may need to be taken care of (for example, non-callable > attributes). > BTW, the copy … [View More]

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Re: [Python-ideas] [Python-Dev] What if replacing items in a dictionary returns the new dictionary?
by Roy Hyunjin Han May 5, 2011

May 5, 2011

>> 2011/4/29 Roy Hyunjin Han <starsareblueandfaraway(a)gmail.com>: >> It would be convenient if replacing items in a dictionary returns the >> new dictionary, in a manner analogous to str.replace(). What do you >> think? >> >> # Current behavior >> x = {'key1': 1} >> x.update(key1=3) == None >> x == {'key1': 3} # Original variable has changed >> >> # Possible behavior >> x = {'key1': 1} >> … [View More]

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