Fast assertions

[roed]

It would be cool to have an assertion that was possible to turn on and off, and that weren't caught by except Exception. For example:

class Assertion_Error(BaseException):
    pass
def assert_(F, msg=None, args=(), kwds={}):
    if not callable(F):
        raise ValueError("Must use a callable")
    if assertions_enabled and not F(*args, **kwds):
        raise Assertion_Error(msg)

One could probably also have msg be lazy as well...