On Thu, May 28, 2015 at 10:16:00AM +0200, Peter Otten wrote:
> Even if you limit yourself to CPython there is another effect: the order of
> execution may not meet one's expectations/requirements:
[snip example]
That's an interesting example, and I can't tell if that's a
problem with your (and my) expectations, or a bug in the context
manager implementation.
PEP 343 clearly warns that the finally clause may not run immediately:
Note that we're not guaranteeing that the finally-clause is
executed immediately after the generator object becomes unused
https://www.python.org/dev/peps/pep-0343/
but the documentation for the with-statement suggests strongly that the
__exit__ method will run immediately after the block is exited, before
any additional code (including before any exception is raised. E.g.:
5. The suite is executed.
6. The context manager’s __exit__() method is invoked. If an
exception caused the suite to be exited, its type, value, and
traceback are passed as arguments to __exit__(). Otherwise,
three None arguments are supplied.
https://docs.python.org/2/reference/compound_stmts.html#the-with-statement
> PS: I'm still looking for a fairly elegant rewrite of the problematic
>
> def lines(files):
> for file in files:
> with open(files) as f:
> yield from f
>
> (see Oscar's comment in
> <https://mail.python.org/pipermail/tutor/2015-May/105448.html>)
Oscar's comment includes a syntax error, which makes it hard to run his
code:
print("__exit__ called")__del__.
I can't even begin to guess what that is supposed to be, and reading the
next few messages in the thread doesn't enlighten.
--
Steve
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