07_ Object-oriented

1. Initial knowledge of object-oriented

1. Python support function + object-oriented two kinds of programming

2. Functional programming, object-oriented programming implementation: E-mail function

Function Type:

def mail (email, message):    print ("Go to Hair")    return true# call function mail ("[email protected]", "good Person")

Object-oriented: Create the class first, and then create the object

# Create Class:    # Method (function in Class)    def mail (self, email, message):    print ("Go to Hair")    return true# Call # 1. Create object, class name () obj = Foo () # 2. Execute method via Object Obj.mail ("[Email protected]", "good Person")

3. Classes and objects

A) Create a class

Class Name Def method name (self, XXXX) pass

b) Create an object

Object = Class name ()

c) Through the object execution method

Object. Method Name (123)

4. Database Example

function type

def fetch (host, username, password, sql):    passdef Create (host, username, password, sql):    passdef Remove (host, Username, password, nid):    passdef Modify (host, username, password, name):    Pass

Object-oriented 1

Class SQLHelper:    def fetch (self, host, username, password, sql):        pass    def create (self, host, username, password, SQL):        pass    def remove (self, host, username, password, nid):        pass    def modify (self, host, Username, password, name):        passobj = SQLHelper ()

Object-Oriented 2

Class SQLHelper:    def fetch (self, SQL):        # Connect database        print (self.hhost)        print (self.uusername)        print ( SELF.PWD)        print (SQL)    def create (self, SQL):        pass    def remove (self, nid):        pass    def modify ( Self, name):        passobj = SQLHelper () obj.hhost = "c1.salt.com" obj.uusername = "Alex" obj.pwd = "123" Obj.fetch ("SELECT * From A ")

Summary

1. Creation and execution of classes and objects

# Create Class class Name: Def method name (self, xxxx):p ass# Create Object object = Class name () # Executes a method object from an object. Method Name (123)

2. When to use object-oriented

When some functions have parameters, object-oriented methods can be used to encapsulate the parameter values one at a time to the object, then to the object to take a value.

2. What the hell is self?

Self is a parameter that Python automatically assigns values to

Which object executes the method, and who is self.

Obj1.fetch ("select * from A") self = = Obj1

Obj2.fetch ("select * from A") Self ==obj2

3. Construction Method __init__

Class has a special method __init__, the class () is automatically executed

Class SQLHelper:    # constructor method __init__,a1,a2,a3 for parameters, receive object Parameters    def __init__ (self, a1, A2, A3):        Print ("Auto-execute init")        self.hhost = A1        self.uusername = A2        self.pwd =a3    def fetch (self, SQL):        pass    def create (self, SQL):        pass    def remove (self, nid):        pass    def modify (self, name):        pass# object, object parameter obj1 = SQLHelper ("c1.salt.com", ' Alex ', ' 123 ') # Execute Object obj1.fetch ("select * from A")

4. Encapsulation of the three main features of object-oriented

Object-oriented three major features: encapsulation, inheritance, polymorphism

Package: Primary

Class Person:    def __init__ (self, name, age, Money):        self.name = name        Self.age = age        Self.money = Money
   def Shopping (self):        Self.money = Self.money-2long = person (' dragon ', ' 1 ') Hu = person (' Tiger ', ' 2 ') Bao = person (' Leopard ', 18 , ten) bao.shopping () print (Bao.money)

Encapsulating objects

Class C1:    def __init__ (self, Name, obj):        self.name = name        self.obj = objclass C2:    def __init__ (self, name , age):        self.name = name        Self.age = Age    def show (self):        print (self.name) # Create object c2_obj, Parameter c2_obj = C2 ( ' AA ', 11) # Create object C1, Parameter 2 is Object c2_obj,c2_obj of name,agec1_obj = C1 ("Alex", C2_obj) # C1_obj under obj ageprint (c1_obj.obj.age, c1_ Obj.obj.name, C1_obj.name)

Package: Final Level

Class C1:    def __init__ (self, Name, obj):        self.name = name        self.obj = objclass C2:    def __init__ (self, name , age):        self.name = name        Self.age = Age    def show (self):        print (Self.name) class C3:    def __init__ ( Self, A1):        Self.money = 123        self.aaa = a1c2_obj = C2 (' C2 ', one) # C2_obj is the C2 type #-name = "AA" #-age = 11c1_obj = C1 ("C1", C2_obj) # c1_obj is the C1 type #-name = "C1" #-obj = C2_objc3_obj = C3 (C1_obj) print (c3_obj.aaa.obj.name) # Use C2_obj to execute Show method C 3_obj.aaa.obj.show () # Print (C3.AAA)

5. Inheritance of three major characteristics of area objects

Python can inherit multiple

5.1 Single Inheritance

Single Inheritance Exercise 1:

Class F1: # parent class, base class    def show (self):        print ("show")    def foo (self):        print (Self.name) class F2 (F1):  # Subclass , derived class    def __init__ (self, name):        self.name = name    def bar (self):        print (' Bar ')    def Show (self): # The parent class and subclass have functions that take precedence to subclass local        print (' f2.show ') obj = F2 (' Alex ') Obj.show () Obj.foo ()

　　

Single Inheritance Exercise 2:

Class S1:    def F1 (self): self        . F2 ()    def F2 (self):        passclass S2 (S1):    def-F3 (self): self        . F1 ()    def F2 (self):        passobj = S2 () obj. F3 () # Execution Result: S2 's f2obj = S1 () obj. F1 () # Execution Result: S1 's F2

Summary: As soon as self is present, go back to the origin and look up from the bottom.

1.5.2 Multiple Inheritance

Multiple inheritance Exercise 1: Simple formatting

Class C1:    def F1 (self):        print ("C1 F1")        Passclass C2:    def f2 (self):        print ("C2 F2")        Passclass C3 (C2,C1):    def f3 (self):        print ("C3 F3")        passobj = C3 () obj.f3 () 1obj.f2 () obj.f1 () # Output results C3 f3c2 f2c1 F1

　　

Multiple inheritance: Multi-layered parent class

Class C0 ():    def f2 (self):        print ("C0.f2") class C1 (C0):    def F1 (self):        print ("C1.f1")        Passclass C2:    def f2 (self):        print ("C2.f2")        passclass C3 (C1,C2):    def f3 (self):        print (" C3.f3 ")        passobj = C3 () obj.f2 () # Output result C0.f2

　　

Class C0 ():    def f2 (self):        print ("C0.f2") class C1 (C0):    def F1 (self):        print ("C1.f1")        Passclass C2 :    def f2 (self):        print ("C2.f2")        passclass C3 (C2,C1):    def f3 (self):        print ("c3.f3")        passobj = C3 () obj.f2 ()

Summary:

Multiple inheritance If there are multiple parent classes, and the top-level classes are not unique, the lookup order is left-to-right, bottom-to-top.

Find order when there is a common top-level parent class

Class c_2 ():    def f2 (self):        print ("C_2.f2") class C_1 (c_2):    def F1 (self):        print ("C_1.f1") class C0 (c_2):    def F1 (self):        print ("C0.f1") class C1 (C0):    def F1 (self):        print ("C1.f1")        Passclass C2 (c_1):    def f2 (self):        print ("C2.f2")        passclass C3 (C1,C2):    def f3 (self):        print ("c3.f3")        passobj = C3 () obj.f2 () # Output result C2.f2

07_ Object-oriented