Python将自己更改为继承的类 [英] Python change self to inherited class

问题描述

我有这种结构:

class Foo:
    def __init__(self, val1):
        self.val1 = val1

    def changeToGoo(self)
        HOW???

class Goo(Foo):
    def __init__(self, val1, val2):
        super(val1)
        self.val2 = val2

a = Foo(1)
a.changeToGoo()

'a'现在是Foo的实例
现在，我想通过使用方法"changeToGoo"将其更改为Goo的实例，并添加其他值.

'a' is now an instance of Foo
now i would like to change it to be an instance of Goo, by using the method "changeToGoo", and add the other value.

这如何在Python中完成?

How can this be done in Python?

我尝试过:

self.__class__ = Goo

但是当我检查时:

type(a)

它仍然是Foo，而不是Goo.

it's still Foo, and not Goo.

推荐答案

在Python 2中，使 Foo 从 object 继承，以使其成为新样式的类:

In Python 2, make Foo inherit from object to make it a new-style class instead:

>>> class Foo(object):
...     def __init__(self, val1):
...         self.val1 = val1
... 
>>> class Goo(Foo):
...     def __init__(self, val1, val2):
...         super(val1)
...         self.val2 = val2
... 
>>> f=Foo(1)
>>> f.__class__
<class '__main__.Foo'>
>>> f.__class__ = Goo
>>> f
<__main__.Goo object at 0x10e9e6cd0>
>>> type(f)
<class '__main__.Goo'>

现在您可以更改 self .__ class __ .在 changeToGoo()方法中:

Now you can change self.__class__. In a changeToGoo() method:

def changeToGoo(self)
    self.__class__ = Goo
    self.val2 = 'some value'

或重复使用 __ init __ :

def changeToGoo(self)
    self.__class__ = Goo
    self.__init__(self.val1, 'some value')

这确实会使您的对象有些奇怪，因为它们会更改身份.变形很少是一个好主意.您可能需要重新考虑用例.

This does make your objects somewhat monstrous, in that they change identity. Shapeshifting is rarely a great idea. You may want to rethink your use case.

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