CODEWITHSUNDEEP
pythonpython-3.xoop
Jai Singhal
Jai Singhal

Reputation: 410

Best way to access class member in a class in Python

I want to know which one is the best way to access the class variable in a class, either by self, or by class name

I have read somewhere that self is only used for accessing the instance variable. But when I tried with the below code, it is one of the same things. Is is it mean that we can use either of them?

class MyClass:
    cls_var = 0 # class variable

    def increment(self, incre):
        self.cls_var += incre
        MyClass.cls_var += incre

    def print_var(self):
        print(self.cls_var) #Choice 1
        print(MyClass.cls_var) # Choice 2


obj1 = MyClass()
obj2 = MyClass()

obj1.increment(5)
obj2.increment(10)

obj1.print_var() #prints 5, 15
obj2.print_var() # prints 15, 15

Upvotes: 1

Views: 506

Answers (2)

Arnav Borborah
Arnav Borborah

Reputation: 11789

You should access a class variable only by class name, since that variable is shared among all classes. Thus, to avoid confusion, one should only access class variables by the name of the class; otherwise it might lead to surprising errors (See the second snippet).

Upvotes: 1

J. Katzer
J. Katzer

Reputation: 107

In my opinion you should use "Choice 2", as the class variable "cls_var" is shared by all instances. So if you do 

ob1.increment(5)

also "ob2.cls_var" gets incremented, but Zen of Python sais that explicit is better than implicit! So do 

MyClass.increment(5)

See: https://docs.python.org/2/tutorial/classes.html#class-and-instance-variables.

Upvotes: 0

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