undefined-local (F823)

Derived from the Pyflakes linter.

What it does

Checks for undefined local variables.

Why is this bad?

Referencing a local variable before it has been assigned will raise an UnboundLocalError at runtime.

Example

x = 1


def foo():
    x += 1

Use instead:

x = 1


def foo():
    global x
    x += 1