pylint-errors

W0631 (undefined-loop-variable)

:x: Problematic code:

data = {'x': 1, 'y': 2, 'z': 3}
for k, v in data.items():
    x = f'key: {k} => value: {v}'
    break

print(x)

:heavy_check_mark: Correct code:

data = {'x': 1, 'y': 2, 'z': 3}
x = None
for k, v in data.items():
    x = f'key: {k} => value: {v}'
    break

print(x)

Rationale:

Used when a loop variable (i.e. defined by a for loop or a list comprehension or a generator expression) is used outside the loop.