In the previous fact, we have seen that Python doesn’t have static keyword. All variables that are assigned a value in class declaration are class variables
We should be careful when changing value of class variable. If we try to change class variable using object, a new instance (or non-static) variable for that particular object is created and this variable shadows the class variables. Below is Python program to demonstrate the same.
python - Sample - python code :
# Class for Computer Science Student
class CSStudent:
stream = 'cse' # Class Variable
def __init__(self, name, roll):
self.name = name
self.roll = roll
# Driver program to test the functionality
# Creating objects of CSStudent class
a = CSStudent("Wiki", 1)
b = CSStudent("Techy", 2)
print "Initially"
print "a.stream =", a.stream
print "b.stream =", b.stream
# This thing doesn't change class(static) variable
# Instead creates instance variable for the object
# 'a' that shadows class member.
a.stream = "ece"
print "\nAfter changing a.stream"
print "a.stream =", a.stream
print "b.stream =", b.streampython tutorial - Output :
Initially a.stream = cse b.stream = cse After changing a.stream a.stream = ece b.stream = cse
We should change class variables using class name only.
python - Sample - python code :
# Program to show how to make changes to the
# class variable in Python
# Class for Computer Science Student
class CSStudent:
stream = 'cse' # Class Variable
def __init__(self, name, roll):
self.name = name
self.roll = roll
# New object for further implementation
a = CSStudent("check", 3)
print "a.tream =", a.stream
# Correct way to change the value of class variable
CSStudent.stream = "mec"
print "\nClass variable changes to mec"
# New object for further implementation
b = CSStudent("carter", 4)
print "\nValue of variable steam for each object"
print "a.stream =", a.stream
print "b.stream =", b.streamOutput:
a.tream = cse Class variable changes to mec Value of variable steam for each object a.stream = mec b.stream = mec