Python中的类或静态变量

所有对象共享类或静态变量。不同对象的实例或非静态变量是不同的（每个对象都有一个副本）。例如，让一个计算机科学专业的学生由CSStudent类表示。该类可能有一个静态变量，其值为所有对象的“cse”。并且类也可能有非静态成员，如name和roll 。在 C++ 和Java中，我们可以使用 static 关键字使变量成为类变量。前面没有 static 关键字的变量是实例变量。有关Java示例，请参见 this，对于 C++ 示例，请参见 this。
Python方法很简单；它不需要静态关键字。

All variables which are assigned a value in the class declaration are class variables. And variables that are assigned values inside methods are instance variables.
 

Python

# Python program to show that the variables with a value
# assigned in class declaration, are class variables
 
# Class for Computer Science Student
class CSStudent:
    stream = 'cse'                  # Class Variable
    def __init__(self,name,roll):
        self.name = name            # Instance Variable
        self.roll = roll            # Instance Variable
 
# Objects of CSStudent class
a = CSStudent('Geek', 1)
b = CSStudent('Nerd', 2)
 
print(a.stream)  # prints "cse"
print(b.stream)  # prints "cse"
print(a.name)    # prints "Geek"
print(b.name)    # prints "Nerd"
print(a.roll)    # prints "1"
print(b.roll)    # prints "2"
 
# Class variables can be accessed using class
# name also
print(CSStudent.stream) # prints "cse"
 
# Now if we change the stream for just a it won't be changed for b
a.stream = 'ece'
print(a.stream) # prints 'ece'
print(b.stream) # prints 'cse'
 
# To change the stream for all instances of the class we can change it
# directly from the class
CSStudent.stream = 'mech'
 
print(a.stream) # prints 'ece'
print(b.stream) # prints 'mech'

输出：

cse
cse
Geek
Nerd
1
2
cse
ece
cse
ece
mech