Note: Data is a constant, using full capitalization naming rules

10.12 Category Attributes

Definition and Characteristics of Attributes of Category 10.12.1

class Car(object):
	age = 18
    def __init__(self,mark,color,price,speed):
        self.mark = mark
        self.color = color
        self.price = price
        self.speed = speed
 Class attributes and instance attributes
 Class attributes: The attributes owned by class objects are shared by class objects and instance objects. There is only one copy in memory. If it is a public class attribute, it can be accessed by class objects and instance objects.
Class attributes: defined inside a class, outside a method, shared by all objects, occupying one share of memory

Access to Attributes of Class 10.12.2

class Car(object):
	age = 18
    def __init__(self,mark,color,price,speed):
        self.mark = mark
        self.color = color
        self.price = price
        self.speed = speed
        
car1 = Car(mark,color,price,speed)
print('The first method: access through class objects')
print(Car.age)
print('The second way is through: instance object access')
print(car1.age)
print('##########################################################################')
//Note:
1,Our Class Attribute Classification: Common Class Attributes, Private Class Attributes, Protecting Class Attributes
2,Private class attributes are not accessible outside the class, including instance objects or class objects.
3,Inside a class, instance methods can be accessed through class objects and instance objects.

Modification of 10.12.3 Category Attributes

class Person(object):
    '''Establish person class,Attributes have name, age, gender, creation method'''
    country = 'China'

    @classmethod
    def changeCountry(cls,newcountry):
        cls.country = newcountry
        print('At this time, the nationality after the amendment is:',cls.country)

    def __init__(self,name,age,gender):
        self.name = name
        self.age = age
        self.gender = gender

    @staticmethod
    def shoeStyle():
        print('many')


print('Class attributes:',Person.country)
zhang = Person('wang',18,'man')
zhang.country = 'Singapore'#Create new dynamic attributes, instance attributes
Person.country = 'South Africa'
print('Class attributes for instance calls:',zhang.country)
print('Class attributes:',Person.country)
Person.changeCountry('Australia')
print(Person.country)
ming = Person('Xiao Ming',18,'boy')
ming.changeCountry('North America')
ming.shoeStyle()
Person.shoeStyle()

//Note:
1,Class attributes are modified by class objects
2,You can't modify it by being an instance object, otherwise you just add a dynamic attribute.( init If there is a field in it, it will be overwritten)

Category 10.13 Methods

Category 10.13.1 Attributes

class Person(object):
    '''Establish person class,Attributes have name, age, gender, creation method'''
    country = 'China'

    @classmethod
    def changeCountry(cls,newcountry):
        cls.country = newcountry
        print('At this time, the nationality after the amendment is:',cls.country)

    def __init__(self,name,age,gender):
        self.name = name
        self.age = age
        self.gender = gender

    @staticmethod
    def shoeStyle():
        print('many')


print('Class attributes:',Person.country)
zhang = Person('wang',18,'man')
zhang.country = 'Singapore'
Person.country = 'South Africa'
print('Class attributes for instance calls:',zhang.country)
print('Class attributes:',Person.country)
Person.changeCountry('Australia')
print(Person.country)
ming = Person('Xiao Ming',18,'boy')
ming.changeCountry('North America')
ming.shoeStyle()
Person.shoeStyle()

//Note:
1,Format of Class Method
@classmethod
def Method name( cls): 
	pass
2,Class properties can be modified
3,It can be accessed either by class objects or by instance objects.