Python類的構造方法及繼承問題

構造方法名字固定為__init__，在創建對象時會自動調用，用於實現類的初始化：

>>> 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('韓曉萌','21')
>>> p.get_name()
'韓曉萌'
>>> p.get_age()
'21'
>>>

如果子類重寫了__init__方法，那么在方法內必須顯式的調用父類的__init__方法：

# 沒有調用父類的__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'

# 調用了父類的__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('楊超越', 21, 'C')
>>> w.get_cup()
'C'
>>> w.get_name()
'楊超越'
>>> w.get_age()
21