### 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<<str<<endl;
}
void f(string str,int times)//输出字符串 times次
{
for(int i=0;i<times;i++)
{
cout<<str<<endl;
}
}
~~~
python实现：
通过参数默认值实现重载
~~~
<span style="font-size:18px;">def f(str,times=1):
print str*times
f('sssss')
f('sssss',10)</span>
~~~
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__()
~~~
