Python notes (13): operations such as object-oriented programming

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Understanding of operational concepts

operation (Operation) Is an abstraction of operational logic

• Operation embodies an operation logic , In a broad sense, any program is an operation
• Python The interpreter reserves a batch of operation interfaces through reservation methods , Overload required
• The reserved method generally corresponds to the operator ,Python The operation in is embodied as the overloading of the operator
• Operation essentially embodies the interaction 、 Include relationships and general operational relationships

Limitation of operation overload

• Cannot overload Python Language built-in type operators
• Cannot create a new operator , Can only be done by overloading
• is,and,not,or Can't be overloaded

operator overloading

Arithmetic operator

• Unary operator ：+、-、~
• Binary operator ：+、-、*、/、//、%、divmod()、pow()、**、<<、>>、&、^、|

Comparison operator

Comparison operator ：<、<=、==、!=、>、>=

The operation overload of two object comparison operations

Members of the operation

• Members get ：[]、def、.reversed()
• Member judgment ：in

Other operations

Python Built in functions ：rep(),str(),len(),int(),flaot,complex(),round(),bytes(),bool(),format(),.format( Common methods )

Python Class polymorphism

polymorphic _(Polymorphism)_ Is for the method , Polymorphism that reflects the flexibility of the method ; To put it simply , It consists of two parts

• Polymorphism of parameter types ： The ability of a method to handle multiple types

  Python Function of / Methods have no type declaration restrictions , Naturally, it supports the polymorphism of parameter types

  Python The idea of programming is ： Document constraints , Not syntactic constraints

  Distinction between different parameter types and functions , Need a programmer to complete

• Parameter form polymorphism ： The ability of a method to accept multiple parameters

  Python Function of / Method can support variable parameters , Support polymorphism in the form of parameters

  Python Class methods are also functions , Various definitions of functions are valid

  Determination of the number of different parameters and default values , It needs to be done by programmers

Polymorphism is OOP A traditional concept ,Python Nature supports polymorphism , No special grammar is needed , The sample code is as follows ：

import abc
class Animal(metaclass=abc.ABCMeta): # The same thing : animal 
    @abc.abstractmethod
    def talk(self):
        pass

class Cat(Animal): # One of the forms of animals : cat 
    def talk(self):
        print('say miaomiao')

class Dog(Animal): # The second form of animals : Dog 
    def talk(self):
        print('say wangwang')

class Pig(Animal): # The third form of animals : The pig 
    def talk(self):
        print('say aoao')
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