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.

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'
   
   with mycontext():
      print 'The bit in the middle'

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 statements.