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.
# 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("Geek", 1) b = CSStudent("Nerd", 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 "
After changing a.stream"print "a.stream =", a.stream print "b.stream =", b.stream |
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.
# 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 "
Class variable changes to mec" # New object for further implementation b = CSStudent("carter", 4) print "
Value of variable steam for each object"print "a.stream =", a.stream print "b.stream =", b.stream |
Output:
a.tream = cse Class variable changes to mec Value of variable steam for each object a.stream = mec b.stream = mec
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