Create APIs that work as decorators and as context managers.
If you’re a library or framework creator then it is nice to be able to create APIs that can be used either as decorators or context managers.
The contextdecorator module is a backport of new features added to the contextlib module in Python 3.2. contextdecorator works with Python 2.4+ including Python 3.
Context managers inheriting from ContextDecorator have to implement __enter__ and __exit__ as normal. __exit__ retains its optional exception handling even when used as a decorator.
from contextdecorator import ContextDecorator class mycontext(ContextDecorator): def __enter__(self): print 'Starting' return self def __exit__(self, *exc): print 'Finishing' return False >>> @mycontext() ... def function(): ... print 'The bit in the middle' ... >>> function() Starting The bit in the middle Finishing >>> with mycontext(): ... print 'The bit in the middle' ... Starting The bit in the middle Finishing
Existing context managers that already have a base class can be extended by using ContextDecorator as a mixin class:
from contextdecorator import ContextDecorator class mycontext(ContextBaseClass, ContextDecorator): def __enter__(self): return self def __exit__(self, *exc): return False
contextdecorator also contains an implementation of contextlib.contextmanager that uses ContextDecorator. The context managers it creates can be used as decorators as well as in with statements.
from contextdecorator import contextmanager @contextmanager def mycontext(*args): print 'Started' try: yield finally: print 'Finished!' >>> @mycontext('some', 'args') ... def function(): ... print 'In the middle' ... Started In the middle Finished! >>> with mycontext('some', 'args'): ... print 'In the middle' ... Started In the middle Finished!
Repository and issue tracker:
The project is available for download from PyPI so it can be easily installed:
pip install -U contextdecoratoreasy_install -U contextdecorator
The tests require unittest2 to run.
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