Python's @ symbol

Python has always been used, did not go to the system to learn, in an interview saw the @ symbol, came back to see, the symbol used in the adorner, used to decorate a function, the modified function as a parameter passed to the adorner, the following examples:

1. @classmethod and @staticmethod

These two meanings are obvious, when defining the method @classmethod means that the method is a class method, the class method must have a parameter of CLS, the class itself, the first argument of the instance method is the [email protected] Adornment method is basically the same as a global function.

Both of these modified methods are available through instance and class invocation.

Class A ():    @classmethod    def CLASSM (CLS):        print "class method, and Invoker:", cls.__name__    @ Staticmethod    def staticm ():        print "static Method" class B (A):    PASSA.CLASSM ()  #class method, and Invoker:AB.classM ()  #class method, and Invoker:BA.staticM () #static methodb.staticm () #static methoda=a () A.CLASSM ()  #class method, and Invoker:Aa.staticM () #static methodb=b () B.CLASSM ()  #class method, and Invoker: BB.STATICM () #static method

　

2. As a normal modifier, the following definition is similar to Testone=func (Testone)

Class C ():    def func (FN):        def Test (*args):            print "Hello"        return test    @func    def testone ( b):        print a**2+b**2    if __name__== "__main__":        testone (3,4) #output: Hello

Class C ():    def func (FN):        def Test (*args):            print "Hello"            fn (*args)        return test    @func    def Testone (A, b):        print a**2+b**2    if __name__== "__main__":        testone (3,4) #output: hello25

3. Unusual notation, used to modify a class, can be used in a single-case mode

Def Singleton (CLS):    instance={}    def getinstance ():        If CLS not in instance:            instance[cls]=cls ()        return INSTANCE[CLS]    return getinstance@singletonclass Myclass:    pass#output>>> my1= Myclass () >>> print my1<__main__. Myclass instance at 0x00000000028c2f48>>>> my2=myclass () >>> print my2<__main__. Myclass instance at 0x00000000028c2f48>

　　

　　

Python's @ symbol