=实例变量（或属性）
在Python中，实例变量是其值在构造函数或方法中使用self分配的变量。

类变量是其值在类中赋值的变量。

# Python program to show that the variables with a value

# assigned in class declaration, are class variables and

# variables inside methods and constructors are instance

# variables.

# Class for Computer Science Student

class CSStudent:

# Class Variable

stream = 'cse'

# The init method or constructor

def __init__(self, roll):

# Instance Variable

self.roll = roll

# Objects of CSStudent class

a = CSStudent(101)

b = CSStudent(102)

print(a.stream) # prints "cse"

print(b.stream) # prints "cse"

print(a.roll) # prints 101

# Class variables can be accessed using class

# name also

print(CSStudent.stream) # prints "cse"