[Python-Dev] Proposed resolutions for open PEP 343 issues (original) (raw)

Guido van Rossum guido at python.org
Sat Oct 22 19:22:56 CEST 2005

On 10/22/05, Nick Coghlan <ncoghlan at iinet.net.au> wrote:

I'm still looking for more feedback on the issues raised in the last update of PEP 343. There hasn't been much direct feedback so far, but I've rephrased and suggested resolutions for the outstanding issues based on what feedback I have received, and my own thoughts over the last week of so.

Thanks for bringing this up again. It's been at the back of my mind, but hasn't had much of a chance to come to the front lately...

For those simply skimming, my proposed issue resolutions are:

1. Use the slot name "context" instead of "with"

+1

2. Reserve the builtin name "context" for future use as described below

+0.5. I don't think we'll need that built-in, but I do think that the term "context" is too overloaded to start using it for anything in particular.

3a. Give generator-iterators a native context that invokes self.close()

I'll have to think about this one more, and I don't have time for that right now.

3b. Use "contextmanager" as a builtin decorator to get generator-contexts

+1

4. Special case the context slot to avoid the need to decorate it

-1. I expect that we'll also see generator functions (not methods) as context managers. The functions need the decorator. For consistency the methods should also be decorated explicitly.

For example, while I'm now okay (at the +0.5 level) with having files automatically behave like context managers, one could still write an explicit context manager 'opening':

@contextmanager def opening(filename): f = open(filename) try: yield f finally: f.close()

Compare to

class FileLike:

def __init__(self, ...): ...

def close(self): ...

@contextmanager
def __context__(self):
    try:
        yield self
    finally:
        self.close()

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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