Decorator and context manager from a single API (Python)

2010-06-27T15:15:01-07:00

Python recipe 577273 by Michael Foord (contextmanager, context_manager, decorator, decorators, with, with_statement). Revision 12.

Create objects that act as both context managers and as decorators, and behave the same in both cases.

Works with Python 2.4 - 2.7 and Python 3. The tests require unittest2 or Python 3.2 to run. (And because the tests use the with statement they won't work with Python 2.4.)

Example:

from contextdecorator import ContextDecorator

class mycontext(ContextDecorator):

    def __init__(self, *args):
        """Normal initialiser"""

    def before(self):
        """
        Called on entering the with block or starting the decorated function.

        If used in a with statement whatever this method returns will be the
        context manager.
        """

    def after(self, *exc):
        """
        Called on exit. Arguments and return value of this method have
        the same meaning as the __exit__ method of a normal context
        manager.
        """

Both before and after methods are optional (but providing neither is somewhat pointless). See the tests for more usage examples.

POSIX context manager to temporarily silence, or filter lines from stdout (Python)

2010-03-03T06:17:23-08:00

Python recipe 577083 by pwaller (contextmanager, freopen, silence, stdout, with). Revision 2.

Fed up with libraries you don't have control over emitting text into your precious stdout?

If they use stdout through python, then you can just change sys.stdout to be something else. If they are printing directly to stdout through a C module, or some other means, then you are stuck.

.. at least until you discover the with silence(): block!

Caveats: Non-portable, tested only on 2.6 under Linux, uses threading.

Example output:

$ python silence_file.py 
Before with block..
Sensible stuff!
After the silence block

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Decorator and context manager from a single API (Python)

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