Five, Python faces 2, variable objects of the class

2, class variables

Description : Reference variable assignment in a class by class or space

class User:
    # 类变量（类空间定义的变量）
    category = '未知类型'
    
# 类变量（通过类引用赋值的变量）
User.type = '普通用户'

1) call a class variable

(1) class by calling the class variables

Description : Gets and can change the value of the variable class by class

class User:
    category = '未知类型'

print(User.category)           # 通过类获取类变量
print('-'*30)

User.category = '改变后的类型'   # 通过类更改类变量
print(User.category)

未知类型
------------------------------
改变后的类型

(2) the object by calling the class variables

Description : Gets the value can only be variable by the object class.

class User:
    category = '未知类型'
    
u = User()
# 当对象本身没有 category 实例变量时，对象可以访问到该类变量
print(u.category)    

未知类型

Note : The Object variable assignment for the new instance variables, not class variables.

class User:
    category = '未知类型'
    
u = User()
u.category = '实例变量'    # 通过对象对变量赋值为新增实例变量

print(u.category)          # 当对象本身有 category 实例变量时，对象有限访问实例变量
print('-'*30)

print(User.category)       # 类变量

2) Operation class variables

Description : Python class class variables may be added or deleted dynamically (dynamic Python's)

• In the class assignment is to increase body type variable is a new variable
• del delete class variables

class Item:
    # 类变量
    itemtype = '电子产品'
    itemcolor = '未知'
    
print('种类：', Item.itemtype)
print('颜色：', Item.itemcolor)
print('-'*30)

Item.price = 100    # 增加新的类变量
print('价钱：', Item.price)

del Item.price     # 删除类变量

种类： 电子产品
颜色： 未知
------------------------------
价钱： 100