Python Object-Oriented basics

Object-Oriented Fundamentals

1. What is object-oriented programming?

-Previously used functions

-Class + Object

2. What is a class and what is an object and what does it matter?

class class: def function 1 (): Pass def function 2 (): Pass # obj is an object that instantiates the process obj = class () obj. function 1 ()　　

========== object-oriented bad ============

========== function Programming Good ==============

-Sometimes, function programming can be implemented? More trouble.

-Object-oriented is very simple to implement.

3. When is an object-oriented application?

-1. When multiple functions have common parameters

-2. Create something based on a template

-3. Link server, execute command, close

Note: Object-oriented, you can make more changes to modify the requirements.

4.self is the object that invokes the current method.

-The function (method) is stored in the class.

-The field is saved under Object memory.

5. Usage scenarios for static fields.

-Each field you create has a common value and can be set as a static field.

Member properties

class Foo: def __init__ (self,name): # normal field, property  =" China "

Global Properties

class Foo: # static fields, public properties  " China "def__init__= name　　

6. Object-oriented three major features, inheritance, encapsulation, polymorphism.

Packaging:

-In-Class encapsulation: Fields, methods

-The value of the normal field is encapsulated in the object:

Example

classF1:def __init__(self,n): self. N=NPrint('F1') classF2:def __init__(SELF,ARG1): SELF.A=arg1Print('F2') classF3:def __init__(SELF,ARG2): self.b=arg2Print('F3') O1= F1 ('Alex') O2=F2 (O1) O3=F3 (O2)########### Output alex:o3.b.a.n############O1 = F1 (' Alex ')#O2 = F2 (O1)#O3 = F3 (O2)#print (O3.B.A.N)#Execution Results#Alex#Note: O3 contains O2 containing O1 containing n assignments for Alex. 

Inherited:

Example:

Find the result: corresponding inheritance.

classF1:def __init__(self):Print('F1')     defA1 (self):Print('F1A1')    defA2 (self):Print('f1a2')  classF2 (F1):def __init__(self):Print('F2')    defA1 (self):Print('F2A1')    defA2 (self): self.a2 ()Print('f2a2')  classF3 (F2):def __init__(self):Print('F3') #def a1 (self):#print (' f3a1 ') defA2 (self):Print('F3A1') obj=F3 () obj.a1 ( )

Polymorphic:

-Python: Default support polymorphism, no type limit

-Polymorphic: Multiple forms.

7. Fields and Methods

Field:

Normal field (saved in object)

Static fields (saved in class)

Method:

Normal method (save in class, caller object, at least one self parameter)

class F1:     ... def A1 (self):         Print  == A1 ()#  Note: obj object memory is not stored in the data and consumes memory.    

Static methods (stored in a class, caller class, without creating an object, can have any parameter):

class F1:    @staticmethod    def  A1 ():        print(self.name) f1.a1 () # Note: equivalent to function @staticmethod. 

Python Object-Oriented basics