Local variable name ... referenced before assignment (F823)

Local variables should be defined before the are referenced.

Anti-pattern

In this example, func attempts to increment my_var while also defining a new local variable called my_var. It is not referencing the my_var variable from the global namespace.

my_var = 0

def func():
    my_var += 1

Best practice

In this example, we use the global statement to indicate that the function func should work on the variable my_var from the global namespace.

my_var = 0

def func():
    global my_var
    my_var += 1