On Sat, May 18, 2019 at 8:17 PM Yonatan Zunger <zunger@humu.com> 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.