Fun with Python decorators

decorators.py

HANDLERS = {}

def handler_decorator(*dargs, **dkwargs):
    '''
    This function is actually a decorator factory.

    It makes decorators that take arguments.
    '''

    print "Ermuhgerd! Erm uh dehcruter!"
    print dargs, dkwargs

    def _handler(func):
        '''
        This is the decorator function.

        It returns a wrapper function, and optionally does other things.
        Let's have it register the wrapped function as a handler.
        '''

        def _wrapped(*args, **kwargs):
            '''
            This is the wrapper function.

            The wrapper has the opportunity to do pre- and post-processing
            on the wrapped function. It could be useful for unpacking request
            arguments and serializing the result to JSON in a server api, for
            instance.
            '''
            print "Ermuhgerd! Erm uh rerrper fehrchun!"

            return func(*args, **kwargs)

        HANDLERS[func.__name__] = _wrapped
        return _wrapped
    return _handler

@handler_decorator('foo', 'baz', word='Hi there!')
def foo(*args, **kwargs):
    '''
    Do something silly.

    '''
    print "ba" + ("z" * kwargs.get('count', 20))

@handler_decorator('car', leet='Wheeeee!')
def bar(*args, **kwargs):
    '''
    Do something serious.

    '''
    print "q" + ("u" * kwargs.get('count', 20)) + "x"

if __name__ == "__main__":
    foo_func = HANDLERS['foo']
    foo_func(count=10)
    foo_func(count=30)

    bar_func = HANDLERS['bar']
    bar_func(count=30)

output

Ermuhgerd! Erm uh dehcruter!
('foo', 'baz') {'word': 'Hi there!'}
Ermuhgerd! Erm uh dehcruter!
('car',) {'leet': 'Wheeeee!'}
Ermuhgerd! Erm uh rerrper fehrchun!
bazzzzzzzzzz
Ermuhgerd! Erm uh rerrper fehrchun!
bazzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
Ermuhgerd! Erm uh rerrper fehrchun!
quuuuuuuuuuuuuuuuuuuuuuuuuuuuuux

Today I used this pattern to refactor an API dispatch routine on a Django server I've been working on (Not on github, it's a private project :)). It's pretty slick!