如何从 Python 中的继承类设置和获取父类属性？
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How to set and get a parent class attribute from an inherited class in Python?
提问by msampaio
I have the Familyand its inherited Personclasses. How do I get the familyNameattribute from the Personclass?
我有Family及其继承的Person类。如何familyName从Person类中获取属性？
class Family(object):
def __init__(self, familyName):
self.familyName = familyName
class Person(Family):
def __init__(self, personName):
self.personName = personName
For instance, let these Familyand Personobjects:
例如，让这些Family和Person对象：
strauss = Family('Strauss')
johaness = Person('Johaness')
richard = Person('Richard')
I'd like to do something such as:
我想做一些事情，例如：
print richard.familyName
and get 'Strauss'. How can I do this?
并得到'Strauss'。我怎样才能做到这一点？
采纳答案by Martijn Pieters
You cannot.
你不能。
Instances only inherit the parent class methods and attributes, not instanceattributes. You should not confuse the two.
实例只继承父类的方法和属性，而不是实例属性。你不应该混淆两者。
strauss.familyNameis an instanceattribute of a Familyinstance. The Personinstances would have their owncopies of the familyNameattribute.
strauss.familyName是实例的实例属性Family。本Person实例将有他们自己的副本familyName属性。
You normally would code the Personconstructor to take two arguments:
您通常会将Person构造函数编码为采用两个参数：
class Person(Family):
def __init__(self, personName, familyName):
super(Person, self).__init__(familyName)
self.personName = personName
johaness = Person('Johaness', 'Strauss')
richard = Person('Richard', 'Strauss')
An alternative approach would be for Personto hold a reference to a Familyinstance:
另一种方法是Person保存对Family实例的引用：
class Person(object):
def __init__(self, personName, family):
self.personName = personName
self.family = family
where Personno longer inherits from Family. Use it like:
其中，Person从不再继承Family。像这样使用它：
strauss = Family('Strauss')
johaness = Person('Johaness', strauss)
richard = Person('Richard', strauss)
print johaness.family.familyName
回答by Lennart Regebro
In addition to Martijns suggestions, you can also create the Person from the Family instance, that way letting the family keep track of it's members:
除了 Martijns 建议，您还可以从 Family 实例创建 Person，这样可以让家庭跟踪其成员：
class Person(object):
def __init__(self, person_name, family):
self.person_name = person_name
self.family = family
def __str__(self):
return ' '.join((self.person_name, self.family.family_name))
class Family(object):
def __init__(self, family_name):
self.family_name = family_name
self.members = []
def add_person(self, person_name):
person = Person(person_name, self)
self.members.append(person)
return person
def __str__(self):
return 'The %s family: ' % self.family_name + ', '.join(str(x) for x in self.members)
Usage like this:
用法如下：
>>> strauss = Family('Strauss')
>>> johannes = strauss.add_person('Johannes')
>>> richard = strauss.add_person('Richard')
>>>
>>> print johannes
Johannes Strauss
>>> print richard
Richard Strauss
>>> print strauss
The Strauss family: Johannes Strauss, Richard Strauss
