Python not defined error when using with block

class fcount(object):
    def __init__(self, func):
            self.func = func
            self.count = 0
            self.context_count = 0
    def __enter__(self):
            self.context_count = 0
    def __call__(self, *args):
            self.count += 1
            self.context_count += 1
            return self.func(*args)
    def __exit__(self, exctype, value, tb):
            return False

This is a decorator. The idea is to keep a separate count when using a 'with' block.

If I do this:

@fcount
def f(n):
    return n+2

with fcount(foo) as g:
    print g(1)

I get this error: TypeError: 'NoneType' object is not callable

I tried printing out the type of g inside that with block, and of course the type is None.

Any idea why g isn't being assigned to fcount(foo)?

This does work:

g = fcount(foo)
with g:
    g(1)