执行父类的构造方法

实例：

class c1:
    def f1(self):
        print("c1.f1")
class c2(c1):
    def f1(self):
        super(c2,self).f1()    #主动执行父类的f1方法，另一种方法：c1.f1(self)，3.0以后的版本尽量不用。
        print("c2.f1")
obj = c2()
obj.f1()

通过继承的方式实现给原代码添加功能而不修改源代码：

1 class Foo:
2     def f1(self):
3         print("Foo.f1")

backend>>commons

 1 from settings import ClassName
 2 from backend import commons
 3 def execute():
 4     cls = getattr(commons, ClassName)       #利用反射
 5     obj = cls()
 6     obj.f1()
 7 
 8 if __name_ == "__main__":
 9     execute()
10 
11 
12 ###########执行lib.py文件，需修改以下内容############
13 from settings import ClassName
14 from settings import path
15 def execute():
16     model = __import__(path, fromlist = True)
17     cls = getattr(model, ClassName)
18     obj = cls()
19     obj.f1
20 
21 if __name_ == "__main__":
22     execute()

index

1 from backend.commons import Foo
2 
3 
4 class MyFoo(Foo):
5     def f1(self):
6         print("before")
7         super(MyFoo, self).f1()     #执行原来的功能
8         print("after")

lib

1 ClassName = "Foo"
2 
3 
4 ###########执行lib.py文件，需修改以下内容#############
5 path = "lib"
6 ClassName = "MyFoo"

settings

实例：

class MyDict(dict):
    def __init__(self):
        self.li = []
        super(MyDict, self).__init__()

    def __setitem__(self, key, value):
        self.li.append(key)
        super(MyDict, self).__setitem__(key, value)

    def __str__(self):
        temp_list = []
        for key in self.li:
            value = self.get(key)                                   #执行原有的字典方法
            temp_list.append("%s:%s" % (key, value))
        temp_str = "{" + ",".join(temp_list) + "}"

obj = MyDict()
obj["K1"] = 123
obj["k2"] = 456
print(obj)

设计模式之单例模式：（用来创建单个实例）

class Foo:
    
    instance = None
    
    def __init__(self):
        self.name = name
        
    @classmethod
    def get_instance(cls):        #cls是类名
        if cls.instance:
            return cls.instance
        else:
            obj = cls("alex")
            cls.instance = obj
            return obj

obj1 =Foo.get_instance()
print(obj1)
obj2 = Foo.get_instance()
print(obj2)