class

最后更新于:2022-04-02 00:35:02

### python class 分为三个部分:class and object(类与对象),inheritance(继承),overload(重载)and override(覆写)。 ### class and object 类的定义,实例化,及成员访问,顺便提一下python中类均继承于一个叫object的类。 ~~~ class Song(object):#definition def __init__(self, lyrics): self.lyrics = lyrics#add attribution def sing_me_a_song(self):#methods for line in self.lyrics: print line happy_bday = Song(["Happy birthday to you", "I don't want to get sued", "So I'll stop right there"])#object1 bulls_on_parade = Song(["They rally around the family", "With pockets full of shells"])#object2 happy_bday.sing_me_a_song()#call function bulls_on_parade.sing_me_a_song() ~~~ ### inheritance(继承) python支持继承,与多继承,但是一般不建议用多继承,因为不安全哦! ~~~ class Parent(object): def implicit(self): print "PARENT implicit()" class Child(Parent): pass dad = Parent() son = Child() dad.implicit() son.implicit() ~~~ ### overload(重载)and override(覆写) 重载(overload)和覆盖(override),在C++,Java,C#等静态类型语言类型语言中,这两个概念同时存在。 python虽然是动态类型语言,但也支持重载和覆盖。 但是与C++不同的是,python通过参数**默认值**来实现函数重载的重要方法。下面将先介绍一个C++中的重载例子,再给出对应的python实现,可以体会一下。 C++函数重载例子: ~~~ void f(string str)//输出字符串str 1次 { cout<def f(str,times=1): print str*times f('sssss') f('sssss',10) ~~~ 覆写 ~~~ class Parent(object): def override(self): print "PARENT override()" class Child(Parent): def override(self): print "CHILD override()" dad = Parent() son = Child() dad.override() son.override() ~~~ **super()函数** **函数被覆写后,如何调用父类的函数呢?** ~~~ class Parent(object): def altered(self): print "PARENT altered()" class Child(Parent): def altered(self): print "CHILD, BEFORE PARENT altered()" super(Child, self).altered() print "CHILD, AFTER PARENT altered()" dad = Parent() son = Child() dad.altered() son.altered() ~~~ python中,子类自动调用父类_init_()函数吗? **答案是否定的,子类需要通过super()函数调用父类的_init_()函数** ~~~ class Child(Parent): def __init__(self, stuff): self.stuff = stuff super(Child, self).__init__() ~~~
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