contextdecorator

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 <http://docs.python.org/library/contextlib.html>_ 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__ <http://docs.python.org/reference/datamodel.html#object.__exit__>_ retains its optional exception handling even when used as a decorator.

Example::

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 <http://docs.python.org/library/contextlib.html#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:

• contextdecorator on google code <http://code.google.com/p/contextdecorator/>_

The project is available for download from PyPI <http://pypi.python.org/pypi/contextdecorator>_ so it can be easily installed:

| ``pip install -U contextdecorator``
| ``easy_install -U contextdecorator``

The tests require unittest2 <http://pypi.python.org/pypi/unittest2>_ to run.