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：

class Foo:
    def f1(self):
        print("Foo.f1")

from settings import ClassName
from backend import commons
def execute():
    cls = getattr(commons, ClassName)       #利用反射
    obj = cls()
    obj.f1()

if __name_ == "__main__":
    execute()


###########执行lib.py文件，需修改以下内容############
from settings import ClassName
from settings import path
def execute():
    model = __import__(path, fromlist = True)
    cls = getattr(model, ClassName)
    obj = cls()
    obj.f1

if __name_ == "__main__":
    execute()

from backend.commons import Foo


class MyFoo(Foo):
    def f1(self):
        print("before")
        super(MyFoo, self).f1()     #执行原来的功能
        print("after")

ClassName = "Foo"


###########执行lib.py文件，需修改以下内容#############
path = "lib"
ClassName = "MyFoo"

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)