What is the Python equivalent of static variables inside a function?

Question

What is the idiomatic Python equivalent of this C/C++ code?

void foo()
{
    static int counter = 0;
    counter++;
          


        

Answer 1

Other solutions attach a counter attribute to the function, usually with convoluted logic to handle the initialization. This is inappropriate for new code.

In Python 3, the right way is to use a nonlocal statement:

counter = 0
def foo():
    nonlocal counter
    counter += 1
    print(f'counter is {counter}')

See PEP 3104 for the specification of the nonlocal statement.

If the counter is intended to be private to the module, it should be named _counter instead.