Python类定义和类继承详解
一、类定义：
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
类的私有属性：
__private_attrs 两个下划线开头，声明该属性为私有，不能在类地外部被使用或直接访问
在类内部的方法中使用时 self.__private_attrs
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
私有的类方法
__private_method 两个下划线开头，声明该方法为私有方法，不能在类地外部调用
在类的内部调用slef.__private_methods
类的专有方法：
__init__ 构造函数，在生成对象时调用
__del__ 析构函数，释放对象时使用
__repr__ 打印，转换
__setitem__按照索引赋值
__getitem__按照索引获取值
__len__获得长度
__cmp__比较运算
__call__函数调用
__add__加运算
__sub__减运算
__mul__乘运算
__div__除运算
__mod__求余运算
__pow__称方
示例:
#类定义
class people:
#定义基本属性
name = ''
age = 0
#定义私有属性,私有属性在类外部无法直接进行访问
__weight = 0
#定义构造方法
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()
二、继承类定义：
1.单继承
class <类名>(父类名) <语句> eg. class childbook(book) age = 10
2.类的多重继承
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
#另一个类，多重继承之前的准备
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))
#多重继承
class sample(speaker,student):
a =''
def __init__(self,n,a,w,g,t):
student.__init__(self,n,a,w,g)
speaker.__init__(self,n,t)
test = sample("Tim",25,80,4,"Python")
test.speak()#方法名同，默认调用的是在括号中排前地父类的方法
类方法的覆写——子类覆盖掉父类的方法
def 方法名与父类一致
若是在方法中要使用到父类方法 父类名.方法名
若是将类放到了模块中
使用时
import A l = A.类()
以上三段程序的执行结果:
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