问题
Possible Duplicate:
defining “boolness” of a class in python
I thought this should print "False", why is it printing "True"?
>>> class Foo(object):
... def __bool__(self):
... return False
...
>>> f = Foo()
>>> if f:
... print "True"
... else:
... print "False"
...
True
>>>
回答1:
You should define __nonzero__() in Python 2.x. It was only renamed to __bool__() in Python 3.x. (The name __nonzero__() actually predates the introduction of the bool type by many years.)
来源：https://stackoverflow.com/questions/8909932/how-to-overload-pythons-bool-method