Python Learning note-day8 (Special method, Iter method, super method, ordered dictionary implementation, Python singleton mode)

Using a special method to implement a dictionary

#Use a class like dictionary dic[' xx ' with brackets in#Brief IntroductionclassFoo:#method called by the ① object [xx]    def __getitem__(self, item):return 'GetItem'    #② Object [XX] = method called by xxx    def __setitem__(self, Key, value):return 'SetItem'    #method called by the ③del object [xx]    def __delitem__(self, key):return 'Delitem'obj=Foo ()#①RET = obj['Test']#②obj['K1'] = 111#③delobj['K1']#ExampleclassFoo:def __getitem__(self, item):#Print (Type (item), item)        #Item.Start item.stop item.step        Print(Type (item))return123def __setitem__(self, Key, value):#Key.start key.stop key.step        Print(Type (key), type (value))def __delitem__(self, key):#Key.start key.stop key.step        Print(Type (key)) obj=Foo ()#incoming Shard, step, it will be a slice objectRET = Obj[1:4:2]Print(ret)

Iter method

# iter Method class Foo:     def __iter__ (self):         yield 1        yield 2= Foo ()#  When an object encounters an iteration (loop), the __iter__ method is accessed   for in obj:    print(item)

Super method

#Super Method: Actively executes the parent class methodclassC1:defF1 (self):Print('c1.f1')        return123classC2 (C1):defF1 (self):#F1 methods for actively executing parent classesRET =Super (C2, self). F1 ()Print('c2.f1')        returnRetobj=C2 () obj.f1 ( )

An ordered dictionary implementation

#ordered dictionary implementations (based on the Dict class)classmydict (dict):def __init__(self):#The list is ordered and an empty list is defined to accept the key valueSelf.li=[]        #__init__ methods for actively executing parent classesSuper (mydict, self).__init__()    def __setitem__(self, Key, value):#when we go to execute dic[' k1 ' = 123, the __setitem__ method is called        #before calling the Dict class, we add the key to the listself.li.append (Key)#__setitem__ methods for actively executing parent classesSuper (mydict, self).__setitem__(Key,value)def __str__(self):#Define aTemp_list = []         forKeyinchSelf.li:value=self.get (Key) Temp_list.append ("'%s ':%s"%(key,value)) Temp_list='{'+','. Join (Temp_list) +'}'        returnTemp_listobj=mydict () obj['K1'] = 123obj['K2'] = 456Print(obj)

= = "{' K1 ': 123, ' K2 ': 456}

Python single-instance mode

#Python Single-instance mode#1. Using the class method to implement#2. Using static fields to implementclassfoo:instance=Nonedef __init__(self,name): Self.name=name @classmethoddefget_instance (CLS):#CLS class name        ifCls.instance:#If the static field instance is True            returncls.instanceElse: obj= CLS ('Alex') Cls.instance= obj#            returnobjobj1=foo.get_instance ()Print(OBJ1)#here, the static field instance value of the class has been changedObj2 =foo.get_instance ()Print(OBJ2)#Obj1 is the same as OBJ2 memory address

Python Learning note-day8 (Special method, Iter method, super method, ordered dictionary implementation, Python singleton mode)