The way of the Python-day 8-polymorphic, class member, singleton mode, exception handling

1. Polymorphism (multiple types)

The manifestation of polymorphism is as follows:

    def func (ARG):         Print (ARG)    func (1)    func ("Alex")    func ([ 11,12,13]    #func can be anything    # but not for C#,java, arguments must specify type 

The disadvantage of polymorphism: In the absence of annotations, it is not known what type of ARG is, what is the use of it. For example, if it is OK to be a list, then you can append (). But I don't know how to use it when I'm not sure.

2. Class members in Object-oriented

1) field

-static field: The code was created when it was loaded and belongs to the class

-Normal field: There are objects to this, belong to the object

class Province:     " China " # static fields, saved in class    def __init__ (self,name):         # stored in the object, this is a normal field, if this function is not called, then this is not in memory

2) method (belongs to Class)

-Common method: definition must have self, execute through object

-static method: @staticmethod, remove self, parameter is optional, executed by class

-Class method: @classmethod, a special form of a static method. Automatic class parameters, executed by class

classProvince:def __init__(self,name): Self.name=namedefShow (self):#Common Methods        Print(self.name) @staticmethod#static methods, 1. Add this, 2. Remove self,3. Parameters are optional    defF1 (arg1):Print(arg1) @classmethod#class method, you must have parameters    defF2 (CLS):#This parameter is passed automatically and is the class name. One of the static methods.         Print(CLS)defF3 (self):returnSelf.name[1]##方法是由对象调用的#obj = Province ("Henan")#obj.show ()##普通方法由对象去调用执行 (method belongs to Class)#PROVINCE.F1 (111) #静态方法, is only related to the class, does not need the object, is called by the class, the same as the function#province.f2 () #类方法, parameter is class name#obj = Province ("Alex")#ret = obj.f3 ()#print (ret)

The way of the Python-day 8-polymorphic, class member, singleton mode, exception handling