Python: static class variables like in Java?

Question

In Java, I can give a class a static variable, here it's counter. I'm incrementing it in the constructor, which gives it the purpose of keeping track of how many objects have been instantiated from this class

class Thing
{
    private static int counter;

    public Thing()
    {
        counter++;
    }

    public static int getCounter()
    {
        return counter;
    }

}

I could then use counter by using (inside of main, or wherever)

int counter = Thing.getCounter()

Is there any way of doing this in Python? I know you can essentially have static class variables/attributes by not giving them an underscore prefix, and then accessing them through Class.attribute (rather than Object.attribute or Object.get_attribute), but is there any way to use a static variable within the class itself, just like I did with the Java example where I used a static class variable inside the constructor? It would make sense for there to be a keyword like 'self' for this, although if there is I've not figured it out

You can access a class variable with Class.attribute from inside a method of the class just like you can from outside the class. — BrenBarn
– BrenBarn, Commented Jun 15, 2016 at 22:32
This SO post from the past likely answers your question too: stackoverflow.com/questions/68645/… — Barry
– Barry, Commented Jun 15, 2016 at 22:34

Cory Kramer · Accepted Answer · 2022-03-13 23:15:40Z

3

class Thing:
    counter = 0

    def __init__(self):
        Thing.counter += 1

    @staticmethod
    def getCounter():
        return Thing.counter

Example

>>> a = Thing()
>>> b = Thing()
>>> Thing.getCounter()
2

edited Mar 13, 2022 at 23:15

answered Jun 15, 2016 at 22:32

Cory Kramer

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2 Comments

user6158787 Over a year ago

Thanks, this all works (I was going to say that you still have to use self in the method arguments, but I tried it without and it works fine, even though it gives me a red underline) I did try this earlier with Thing as the prefix, but I guess it didn't work because I was also changing the self in the method arguments to Thing as well.

Jan Christoph Terasa Over a year ago

getCounter is not an instance method, but a class method, hence you don't need (and want) self to be the first argument. Be careful, that contrary to most other OO languages a and b will have their own counter variable, so a.counter is different from Thing.counter!

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