Python full Stack development "the 15th" object-oriented three major features--encapsulation

1. Package:

What is encapsulation? (Encapsulation is not a pure meaning of the hidden, in fact, it can still be viewed)

is to hide something that you don't want others to see.

Encapsulating data: Purpose is to protect privacy

Functional encapsulation: Designed to isolate complexity

If you use private, the deformed property cannot be used directly outside of the class, but can be used directly inside the class

# object name. Three ways to take the value of a property name 1. Use self in our usual __init__ method class Course: #恰好给我们提供了实现这种思路的方法 #             #一种思路, Python    def __init__ (self , price,period,name):        self.price = Price        Self.period = period        Self.name = Namec = Course (+, ' Linux ', ' 6 Months ') print (C.period) 2. Define an empty dictionary inside the class, and then load the dictionary with the value def course (price,name, period):    dic = {}    dic[' price '] = Price    dic [' name '] = name    dic [' period '] = period    return DICC = Course (+, ' python ', ' 6 months ') print (c.period) c10/> #对象名. Property name     View the value of the property 3. Take advantage of the Namedtuple method from collections import namedtuple  #只有属性没有方法的类Course = Namedtuple (' Course ', [' name ', ' price ', ' period ']) #传两个参数, the first is a custom name, and the second goes in the property Python = Course (' python ', 10000, ' 6 moths ')  # Equivalent to instantiation of print (Python.name)

2. Encapsulating a private property of a class property (that is, the Class property is preceded by __)

#类属性1class Goods:    # In accordance with the 80 percent calculation (defined a private class property)    __discount = 0.8  #变形后: _goods__discount    def __init__ (self, Name,price):        self.name = name        Self.price = Price    def goods_price (self):        return  self.price * goods . __discountapple = Goods (' Apple ') print (Apple.goods_price ()) # Print (goods.__dict__)  #类名. __dict__print (Goods . _goods__discount)

#类属性的私有方法 # Package: Hide what you don't want to see # Data encapsulation: Purpose to protect privacy class Teacher:    __school = ' Oldboy '  #类属性    def __init__ (self,name , salary):        self.name = name self        . __salary  =  salary  #_Teacher__salary            # Teacher's property   value        #怎么把薪水隐藏起来?        self.__salary=salary    def foo (self):        print ('------') t=teacher (' Egon ', +) print (t.__dict__) # Print (t.name) print (t._teacher__salary) #让显示出来print (teacher._teacher__school)  #类属性使用_类名__属性名t. Foo () # In this class can be called normal # in this class must be called with the _ Class name __ property name (but not recommended)

　　

3. Encapsulating private properties of class objects

Adult BMI: Too light: Less than 18.5 normal: 18.5-23.9 overweight: 24-27 obese: 28-32 very obese, higher than 32 body mass index (BMI) = weight (kg) ÷ height ^2 (m) ex:70kg÷ (1.75x1.75) =22.86

# calculates the BMI, the standard for measuring human health (private property of an object) class Person:def __init__ (Self,height,weight, Name,sex): self.__height = height #私有属性 (let you no longer tune it out) # in this class can be called, outside the class can not call the self . __weigth = Weight Self.__name = name Self.__sex = Sex def tell_bmi (self): #体重指数 return Self.__we   Igth/self.__height * * 2 #在本类中可以调用 def tell_height (self): print (self.__height) def tell_weight (self):             #告诉体重 return self.__weigth def set_weigth (self,new_weight): #修改体重 if New_weight >20: Self.__weigth = new_weight else:raise TypeError (' You are too thin, thin even the number of pounds (fast) No ') #如果体重小于20或者负的, on the initiative to prompt an error egg = Per Son (1.6,96, ' Haiyan ', ' female ') print (Egg.tell_bmi ()) # egg.__height #在类外不能调用 # print (egg._person__height) # View outside the class call print (egg.__dict__) #查看变形后的类型 # egg.set_weigth ( -10) # Print (Egg.tell_weigth ()) Egg.set_weigth (66) # Modified weight of 66print (Egg.tell_weight ()) 

# Private properties of object properties Two class people:    def __init__ (self,name,age,sex,height):        self.__name = name        Self.__age = Age        self.__sex = sex        self.__height = height    def tell_name (self):  #看人名字        Print (self.name)    def set _name (self,val): #修改名字        if not isinstance (Val, str):            raise TypeError (' name must be String type ')        Self.__name = val    def tell_info (self):         print ("           ---------%s info-----------           name:%s           age:%s           sex:%s           height:%s "% (self.__name,self.__name,self.__age,self.__sex,self.__height)) P=people (' Egon ', +, ' male ', ' ') P.tell_info () p.set_name (' Haiyan ')   #调用修改名字的方法p. Tell_info () # Print (p._people __name) #就可以看到了

　　

4. Encapsulating private properties of a class method

Private property of the class method the private property of the # method class Parent:    def __init__ (self):        self.__func ()  #__func ==_parent__func    def __ Func (self):        print (' parent func ') class Son (parent):    def __init__ (self):        self.__func ()  #_Son__func    def __func (self):        print (' son func ')    def _parent__func (self):        print (' son _parent__func ') s = Son () Print (parent.__dict__)  #类名. __dict__ look at the results of the transformation # Private properties: In this class is a normal call #           in this class must be called with the _ Class name __ property name (but not recommended)

#方法的私有属性2class Foo:    def __func (self):        print ("From Foo") class Bar (Foo):    def __func (self):        print ( ' From bar ') B = Bar () B._foo__func () B._bar__func ()

#装饰方法的私有属性3class Foo:    def __init__ (self,height,weight):        self.height = height        self.weight = weight    def __heightpow (self):  #私有方法        return self.height * self.height    def tell_bmi (self):        return Self.weight /self.__heightpow () Egon = Foo (1.7,120) print (EGON.TELL_BMI ()) print (foo.__dict__) print (Egon._foo__heightpow ())  #虽说是私有的, but you can still see it.

5.property

Why use the property: After the function of a class is defined as an attribute, when the object is used again obj.name, it is impossible to realize that its name is executed a function and then calculated, the use of this feature follows the principle of unified access

1. Calculate the area and perimeter of a circle

From math import Piclass Circle:    def __init__ (Self,radius):        Self.radius = Radius    @property  # Adorner: A method is used as a property with    def area (self):        return Self.radius * self.radius* pi    @property    def peimeter (self):        return 2*PI*SELF.RADIUSC = Circle print (c.area)  #当成一个属性来调了, no brackets are used for print (c.peimeter)

2. Caching Web page information

From urllib.request import Urlopenclass web_page:    def __init__ (self,url):        self.url = URL        self.__ Content = None  #内容设置为None    @property    def content (self):        if self.__content:  #如果不为空, that means it has been downloaded  _web_page__content            return self.__content        else:            self.__content = Urlopen (Self.url). Read () #做缓存            return self.__contentmypage = Web_page (' http://www.baidu.com ') print (mypage.content) print (mypage.content) Print (mypage.content)

3. Sum, average, maximum, minimum

Class Num:    def __init__ (Self,*args):        print (args)        if Len (args) ==1 and (type (args[0]) is List or type (Args[0] ) is a tuple):            Self.numbers=args[0]        else:            self.numbers = args    @property    def sum (self):        return SUM (self.numbers)    @property    def avg (self):        return Self.sum/len (self.numbers)    @property    def min (self):        return min (self.numbers)    @property    def max (self):        return max (self.numbers) num = Num ([3,1,3]) VVV = num (8,2,3) print (num.sum) print (num.min) print (num.avg) print (Num.max) print ('-----------') print ( vvv.sum) print (vvv.min) print (vvv.avg) print (Vvv.max)

6.setter

#买东西class Goods:    __discount = 0.8  #类的私有属性    def __init__ (self,name,price):        self.name = name        self._ _price = Price    @property    def Price (self):        # if Hasattr (self, ' __price '):            return Self.__price * goods.__ Discount        # Else:        #     raise Nameerror    @price. Setter    def Price (Self,new_price):        If Type ( New_price) is int:            self.__price = New_price    @price. Deleter    def Price (self):        del self.__ Priceapple = Goods (' Apple ', #) # print (apple.price) Apple.price = 20print (apple.price) # del apple.price# print ( Apple.price) # Apple.set_price ($) # Apple._goods__apple

@property to disguise a method in a class as a property
Turns out to be Obj.func ()
Now is Obj.func---  properties
1. Because properties cannot be modified
So I used @funcname.setter.

Obj.func = New_value is called by the @funcname.setter Adorner decoration method
The method name to be decorated by @property must have the same name as the method decorated by @funcname.setter
2. Another method can be modified, but the last method is called by a method in a class disguised as a property, and this method
Or the same as the original instantiation call
For example:

Class people:    def __init__ (self,name,age,sex,height):        self.__name = name        Self.__age = Age        Self.__sex = Sex        self.__height = height    def tell_name (self):  #看人名字        Print (self.name)    def set_name (Self,val) : #修改名字        if not isinstance (Val, str):            raise TypeError (' name must be String type ')        Self.__name = Val    def tell_info ( Self):         print ("           ---------%s info-----------           name:%s           age:%s           sex:%s           height:%s '"% ( self.__name,self.__name,self.__age,self.__sex,self.__height)) p=people (' Egon ', ' + ', ' male ', ' [+] ') p.tell_info () P.set_name (' Haiyan ')   #调用修改名字的方法p. Tell_info () # Print (p._people__name) #就可以看到了

　　

Python full Stack development "the 15th" object-oriented three major features--encapsulation