What Eric Fahlgren wants is basically the deprecated contextlib.nested function, that function should have the right semantics. See https://github.com/python/cpython/blob/2.7/Lib/contextlib.py#L88-L129
On Wed, Nov 13, 2019 at 6:55 PM Chris Angelico <ros...@gmail.com> wrote: > On Thu, Nov 14, 2019 at 8:48 AM Eric Fahlgren <ericfahlg...@gmail.com> > wrote: > > I have used 'with' for so long that I was under the impression that the > as-target was just a name as in MRAB's simplified syntax above, so imagine > my surprise when I tried putting parentheses around the target and didn't > get a syntax error straight away. I of course had to explore a bit, and > came up with this. The ugly formatting of the with is simply to show that > the parens behave as expected. > > class opener: > > def __init__(self, *files): > > self.files = [open(file) for file in files] > > def __enter__(self): > > return [file.__enter__() for file in self.files] > > def __exit__(self, *exc_info): > > for file in self.files: > > file.__exit__(*exc_info) > > return True > > > > with opener( > > 'x', 'y', 'z' > > ) as ( > > f1, f2, f3 > > ): > > print(f1) > > print(f1.closed) > > print(f2) > > print(f3) > > > > print(f1.closed) > > Note that the semantics here are NOT the same as the semantics of > either ExitStack or a single large 'with' statement. (And I'm not sure > whether or not those two are the same.) With your opener, you first > open each file, then enter each file; and only then are you considered > to be inside the context. With a large 'with' statement, they should > (I believe) be opened and entered individually. If one of the files > fails to open, your constructor will fail, and self.files won't be set > - you won't exit each of the files that you *did* open. > > ChrisA > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/RT3RFVV7KRZ2Z6G2CI3GLHCFLTDUS6DG/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- Sebastian Kreft
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/ZOUTPHHTNZ2EEZZNNSMVHGIP5CSYLVXQ/ Code of Conduct: http://python.org/psf/codeofconduct/
