[issue40235] confusing documentation for IOBase.__exit__

[Daniel Holth]

New submission from Daniel Holth <dholth at fastmail.fm>:

The io documentation says:

IOBase is also a context manager and therefore supports the with statement. In this example, file is closed after the with statement’s suite is finished—even if an exception occurs:

with open('spam.txt', 'w') as file:
    file.write('Spam and eggs!')


I read this to mean that my own subclass of io.BufferedIOBase would call close() when used as a context manager.

Instead, it is necessary to provide an implementation of __exit__ that calls close() to get this behavior.

The documentation lists Mixin Methods, but I couldn't find a definition of the term "Mixin Methods" in the docs.

----------
components: IO
messages: 366032
nosy: dholth
priority: normal
severity: normal
status: open
title: confusing documentation for IOBase.__exit__
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40235>
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