Python：如何通过派生类实例访问父类对象？
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Python: How to access parent class object through derived class instance?
提问by PyNewbie
I'm sorry for my silly question, but... let's suppose I have these classes:
我很抱歉我的愚蠢问题，但是......让我们假设我有这些课程：
class A():
msg = 'hehehe'
class B(A):
msg = 'hohoho'
class C(B):
pass
and an instance of B or C. How do I get the variable 'msg' from the parent's class object through this instance? I've tried this:
和 B 或 C 的实例。如何通过此实例从父类对象中获取变量“msg”？我试过这个：
foo = B()
print super(foo.__class__).msg
but got the message: "TypeError: super() argument 1 must be type, not classobj".
但收到消息：“类型错误：super() 参数 1 必须是类型，而不是 classobj”。
回答by Tim Dumol
You actually want to use
你实际上想使用
class A(object):
...
...
b = B()
bar = super(b.__class__, b)
print bar.msg
Base classes must be new-style classes (inherit from object)
基类必须是新式类（继承自object）
回答by kennytm
If the class is single-inherited:
如果类是单继承的：
foo = B()
print foo.__class__.__bases__[0].msg
# 'hehehe'
If the class is multiple-inherited, the question makes no sense because there may be multiple classes defining the 'msg', and they could all be meaningful. You'd better provide the actual parent (i.e. A.msg). Alternatively you could iterate through all direct bases as described in @Felix's answer.
如果类是多重继承的，这个问题就没有意义，因为可能有多个类定义了“msg”，而且它们都可能是有意义的。你最好提供实际的父级（即A.msg）。或者，您可以按照@Felix的回答中的描述遍历所有直接基础。
回答by John La Rooy
Not sure why you want to do this
不知道你为什么要这样做
>>> class A(object):
... msg = 'hehehe'
...
>>> class B(A):
... msg = 'hohoho'
...
>>> foo=B()
>>> foo.__class__.__mro__[1].msg
'hehehe'
>>>
回答by Olivier Verdier
Try with:
尝试：
class A(object):
msg = 'hehehe'
EDIT:
编辑：
For the 'msg' attribute you would need:
对于 'msg' 属性，您需要：
foo = B()
bar = super(foo.__class__, foo)
print bar.msg
回答by Felix Kling
As msgis a class variable, you can just do:
作为msg类变量，您可以这样做：
print C.msg # prints hohoho
If you overwrite the variable (as you do in class B), you have to find the right parent class. Remember that Python supports multiple inheritance.
如果覆盖变量（就像在 class 中所做的那样B），则必须找到正确的父类。请记住，Python 支持多重继承。
But as you define the classes and you now that Binherits from Ayou can always do this:
但是当您定义类并且B继承自A您的类时，您始终可以这样做：
class B(A):
msg = 'hohoho'
def get_parent_message(self):
return A.msg
UPDATE:
更新：
The most reliable thing would be:
最靠谱的应该是：
def get_parent_attribute(instance, attribute):
for parent in instance.__class__.__bases__:
if attribute in parent.__dict__:
return parent.__dict__[attribute]
and then:
接着：
foo = B()
print get_parent_attribute(foo, 'msg')
回答by Amarghosh
#for B() you can use __bases__
print foo.__class__.__bases__[0].msg
But this is not gonna be easy when there are multiple base classes and/or the depth of hierarchy is not one.
但是当有多个基类和/或层次结构的深度不是一个时，这并不容易。
