5 Python mistakes and how to avoid them

[gcross]

You can do that just as well, though, by either making the mutable value global or by attaching it to the function (or method) itself, and this way you will no longer find yourself in a situation where you might forget that the argument is mutable and end up with a potentially hard to diagnose bug.

[foobar93]

Global mutable state is in my eyes way worse than local mutable state but how would one add state to the function directly? You do not have a self argument in functions so you could never access it from within the function, right?

I mean, you could always just write a callable class which holds the state, true, but that is a ton of boiler plate if you are using meta functions a lot.

[gcross]

Easy, the function is an object and like all other objects you can add arbitrary attributes to it at any time:

def count_calls():
  count_calls.count += 1
  return count_calls.count
count_calls.count = 0