类的相关判断函数

检查obj是否是类cls的对象

class Foo():
    print 'foo'

demo=Foo()

print isinstance(demo,Foo)

检查sub类是否是 super 类的派生类

class Foo():
    print 'foo'

class sub_Foo(Foo):
    print 'sub_Foo'

print issubclass(sub_Foo,Foo)