python 类和类的继承

本文主要介绍了Python类定义和类继承及类的私有属性、类的方法
1.类的定义

class<类名>：
    <语句>

类实例化后，可以使用其属性，实际上，创建一个类之后，可以通过类名访问其属性
如果直接使用类名修改其属性，那么将直接影响到已经实例化的对象

类的方法
在类地内部，使用def关键字可以为类定义一个方法，与一般函数定义不同，类方法必须包含参数self,且为第一个参数
实例如下：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author :Alvin.xie
# @Time :2017-11-06 17:17
# @file :class2.py


#类定义
class people:
    name = ''
    age = 0
    _weight = 0
    def __init__(self,n,a,w):
        self.name = n
        self.age =a
        self._weight =w
    def speak(self):
        print ("%s is speaking: I am %d years old" %(self.name,self.age))


p = people('tom',10,30)
p.speak()

运行结果:
tom is speaking: I am 10 years old
2.类的继承
2.1 单继承

class <类名>(父类名)
    <语句>

eg.
class childbook(book)
    age = 10

2.2 多重继承

class 类名(父类1,父类2,....,父类n)
    <语句1>

需要注意圆括号中父类的顺序，若是父类中有相同的方法名，而在子类使用时未指定，python从左至右搜索,即方法在子类中未找到时，从左到右查找父类中是否包含方法

实例如下：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author :Alvin.Xie
# @Time :2017/11/6 22:41
# @File :class1.py


# 类定义
class People:
    name = ''
    age = 0
    _weight = 0
    _grade = 0

    def __init__(self, n, a, w, g):
        self.name = n
        self.age = a
        self._weight = w
        self._grade = g

    def speak(self):
        print ("%s is speaking: I am %d years old" % (self.name, self.age))


p = People('tom', 10, 30, 1)
p.speak()


class Speaker():
    topic = ''
    name = ''

    def __init__(self, n, t):
        self.name = n
        self.topic = t

    def speak(self):
        print ("I am %s,I am a speaker!My topic is %s" % (self.name, self.topic))


test = Speaker('Tim', 'Python')
test.speak()


# 多重继承
class Sample(Speaker, People):
    a = ''
    # _grade = 4

    def __init__(self, n, a, w, g, t):
        People.__init__(self, n, a, w, g)
        Speaker.__init__(self, n, t)
        print ("I am %s,I am %d years old,and I am %d, I am in grade %d and my topic is %s" % (self.name, self.age, self._weight, self._grade, self.topic))


test = Sample('Ken', 25, 80, 4, 'python')

执行结果：
tom is speaking: I am 10 years old
I am Tim,I am a speaker!My topic is Python
I am Ken,I am 25 years old,and I am 80, I am in grade 4 and my topic is python