Python新式类和旧式类的区别
Python2和Python3中的新式类、经典类(旧式类)的区别
基本概念
python2.x中默认都是经典类，只有显示继承了object的才是新式类
class Person(object): # 新式类
pass
class Person(): # 经典类
pass
class Person: # 经典类
pass
python3.x中取消了经典类，默认都是新式类，不用继承object也是新式类
# 都是新式类写法，并无区别
class Person(object):
pass
class Person():
pass
class Person:
pass
多继承的调用顺序
以下代码是python2.x中的
经典类多继承搜索顺序（深度优先）：当继承多个父类的时候从左到右深度搜索需要的属性，如果父类没有，就去父类的父类中查找，如果没有再从继承的下一个父类中查找。深度优先就是把一个继承的父类一直往深度去查找。
class A:
def __init__(self):
self.n = "A"
class B(A):
def __init__(self):
super(B, self).__init__()
self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
def __init__(self):
super(D, self).__int__()
self.b = "D"
d = D()
print(d.n) # 输出D
注释D中的代码，获得B
class A:
def __init__(self):
self.n = "A"
class B(A):
def __init__(self):
super(B, self).__init__()
self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出B
注释B中的代码，获得A
class A:
def __init__(self):
self.n = "A"
class B(A):
pass
# def __init__(self):
# super(B, self).__init__()
# self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出A
注释A中的代码，获得C
class A:
pass
# def __init__(self):
# self.n = "A"
class B(A):
pass
# def __init__(self):
# super(B, self).__init__()
# self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出C
新式类多继承的搜索顺序（广度优先）：当继承多个父类的时候从左到右广度搜索需要的属性，如果父类没有，就去继承的下一个父类中查找，广度优先其实就是广泛的从继承的父类中查找，不往深度去查找。
class A(object):
def __init__(self):
self.n = "A"
class B(A):
def __init__(self):
super(B, self).__init__()
self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
def __init__(self):
super(D, self).__int__()
self.b = "D"
d = D()
print(d.n) # 输出D
注释D中的代码获得B
class A(object):
def __init__(self):
self.n = "A"
class B(A):
def __init__(self):
super(B, self).__init__()
self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出B
注释B中的代码获得C
class A(object):
def __init__(self):
self.n = "A"
class B(A):
pass
# def __init__(self):
# super(B, self).__init__()
# self.n = "B"
class C(A):
def __init__(self)：
self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出C
注释C中的代码获得A
class A(object):
def __init__(self):
self.n = "A"
class B(A):
pass
# def __init__(self):
# super(B, self).__init__()
# self.n = "B"
class C(A):
# def __init__(self)：
# self.n = "C"
class D(B, C):
pass
# def __init__(self):
# super(D, self).__int__()
# self.b = "D"
d = D()
print(d.n) # 输出A
多继承
class Food(object):
def __init__(self, name, color):
self.name = name
self.color = color
def eatable(self):
print("%s can be eaten." % self.name)
def appearance(self):
print('The color of the %s is %s.' % (self.name, self.color))
class Fruits(object):
def __init__(self, name, nutrition):
self.name = name
self.nutrition = nutrition
def info(self):
print("%s can supply much %s." % (self.name, self.nutrition))
class Salad(Fruits, Food): # 继承多个父类
def __init__(self, name, nutrition, color, tasty):
super(Salad, self).__init__(name, nutrition)
Food.__init__(self, name, color)
self.tasty = tasty
def taste(self):
print("%s is a little %s." % (self.name, self.tasty))
obj = Salad('orange', 'VC', 'orange', 'sour')
obj.eatable()
obj.appearance()
obj.info()
obj.taste()
supper()函数为新式类的方法，采用新式类要求最顶层的父类一定要继承于object，这样就可以用super()函数来调用父类的init()等函数。每个父类都执行且执行一次，并不会出现重复调用的情况。采用super()方法时，会自动找到第一个多继承中的第一父类。
但是如果想要继续调用其它父类init()函数或两个父类的同名函数时，就要用经典类的调用方法了，即 父类名.init(self,参数），如上例
总结
1、新式类继承object类，经典类不继承任何类
2、新式类用super关键字继承构造方法，经典类用 父类.init（self）来继承
3、新式类：广度优先查询，经典类：深度优先查询(因为新式类讲究的是新，所以要找最近的，最新的；然后经典的讲究古老，所以更远更深的)
4、值得注意的是，上面是在python2中做的，在python3中不管是经典类还是新式类，都是采用的是广度优先查询，已经废弃2中的深度查询了