Python Language 创建用户定义的方法对象

获取类的属性(可能通过该类的实例),如果该属性是用户定义的函数对象,未绑定的用户定义的方法对象或类方法对象,则可以创建用户定义的方法对象。

class A(object):
    # func: A user-defined function object
    #
    # Note that func is a function object when it's defined,
    # and an unbound method object when it's retrieved.
    def func(self): 
        pass

    # classMethod: A class method
    @classmethod
    def classMethod(self):
        pass

class B(object):
    # unboundMeth: A unbound user-defined method object
    #
    # Parent.func is an unbound user-defined method object here,
    # because it's retrieved.
    unboundMeth = A.func

a = A()
b = B()

print A.func
# output: <unbound method A.func>
print a.func
# output: <bound method A.func of <__main__.A object at 0x10e9ab910>>
print B.unboundMeth
# output: <unbound method A.func>
print b.unboundMeth
# output: <unbound method A.func>
print A.classMethod
# output: <bound method type.classMethod of <class '__main__.A'>>
print a.classMethod
# output: <bound method type.classMethod of <class '__main__.A'>>

当属性是用户定义的方法对象时,仅当从中检索它的类与存储在原始方法对象中的类相同或派生类时,才会创建新方法对象;否则,原始方法对象按原样使用。

# Parent: The class stored in the original method object
class Parent(object):
    # func: The underlying function of original method object
    def func(self): 
        pass
    func2 = func

# Child: A derived class of Parent
class Child(Parent):
    func = Parent.func

# AnotherClass: A different class, neither subclasses nor subclassed
class AnotherClass(object):
    func = Parent.func
    
print Parent.func is Parent.func                # False, new object created
print Parent.func2 is Parent.func2              # False, new object created
print Child.func is Child.func                  # False, new object created
print AnotherClass.func is AnotherClass.func    # True, original object used