Python 3.6+contextlibterm

contextlib.AbstractContextManager

protocols

The abstract base class of context managers (the __enter__/__exit__ protocol); any class with these methods is its virtual subclass.

Syntax

class C(contextlib.AbstractContextManager): ...

Inheriting is a convenience, not a requirement: issubclass succeeds for any class defining __enter__ and __exit__, so your own manager needs no base class at all. What subclassing buys you is a ready __enter__ that returns self, leaving only __exit__ to write, plus a clean name to use in type hints. Async managers are not covered here — they have their own AbstractAsyncContextManager.

Examples

import contextlib
class CM:
    def __enter__(self): return self
    def __exit__(self, *a): return False
print(issubclass(CM, contextlib.AbstractContextManager))   # → True

See also

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