Python中对象的布尔值

请参阅Python文档

__nonzero__

class foo(object):    def __nonzero__( self) :        return self.bar % 2 == 0def a(foo):    if foo:        print "spam"    else:        print "eggs"def main():    myfoo = foo()    myfoo.bar = 3    a(myfoo)if __name__ == "__main__":    main()