Python类的构造方法及继承问题

构造方法名字固定为__init__，在创建对象时会自动调用，用于实现类的初始化：

>>> class Person:
...     def __init__(self, name, age=0):
...             self.name = name
...             self.age = age
...     def get_name(self):
...             return self.name
...     def set_name(self, name):
...             self.name = name
...     def get_age(self):
...             return self.age
...     def set_age(self, age):
...             self.age = age
...
>>> p = Person('韩晓萌','21')
>>> p.get_name()
'韩晓萌'
>>> p.get_age()
'21'
>>>

如果子类重写了__init__方法，那么在方法内必须显式的调用父类的__init__方法：

# 没有调用父类的__init__方法
>>> class Man(Person):
...     def __init__(self, length):
...             self.length = length
...     def get_length(self):
...             return self.length
...     def set_length(self, length):
...             self.length = length
...
>>> m = Man('18cm')
>>> m.get_length()
'18cm'
>>> m.get_name()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 6, in get_name
AttributeError: 'Man' object has no attribute 'name'

# 调用了父类的__init__方法
>>> class Woman(Person):
...     def __init__(self, name, age=0, cup='A'):
...             super().__init__(name, age)
...             self.cup = cup
...     def get_cup(self):
...             return self.cup
...     def set_cup(self, cup):
...             self.cup = cup
...
>>> w = Woman('杨超越', 21, 'C')
>>> w.get_cup()
'C'
>>> w.get_name()
'杨超越'
>>> w.get_age()
21