Boolean value of objects in Python

Question

As we know, Python has boolean values for objects: If a class has a __len__ method, every instance of it for which __len__() happens to return 0 wi

Answer 1

Refer to the Python docs for __nonzero__.

class foo(object):
    def __nonzero__( self) :
        return self.bar % 2 == 0

def a(foo):
    if foo:
        print "spam"
    else:
        print "eggs"

def main():
    myfoo = foo()
    myfoo.bar = 3
    a(myfoo)

if __name__ == "__main__":
    main()