On Sat, May 18, 2019 at 8:17 PM Yonatan Zunger <[email protected]> wrote:
> Instead, we should permit any expression to be used. If a value does not
> expose an __enter__ method, it should behave as though its __enter__
> method is return self; if it does not have an __exit__ method, it should
> behave as though that method is return False.
>
I'm not sure why you would want this. But it is really easy to implement
with a named function already. I think it would be better to experiment
with a wrapper function first, maybe put it on PyPI, before changing the
language for something whose purpose is unclear (to me).
I think you probably mean something other than what you actually write. It
doesn't really make sense for "any expression" as far as I can tell. What
would it possibly mean to write:
with (2+2) as foo:
print(foo)
But anyway, my toy simple implementation which satisfies the stated
requirement:
>>> from contextlib import contextmanager
>>> @contextmanager
... def zungerfy(obj):
... if hasattr(obj, '__enter__'):
... yield obj.__enter__()
... else:
... yield obj
... if hasattr(obj, '__exit__'):
... obj.__exit__()
...
>>> with zungerfy(Foo(42)) as foo:
... print("Hello", foo.val)
...
...
Hello 42
>>> with zungerfy(open('README.md')) as foo:
... print("Hello", foo.readline())
...
Hello ## About the course
--
Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons. Intellectual property is
to the 21st century what the slave trade was to the 16th.
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