unboundlocalerror local variable 'result' referenced before assignment

Question

This error was asked many times but I can't solve my problem by reading them. My code is:

def show_preference_list_isolated(isolated):
    preference_list_isolated = {
    (240, 323): [(164, 108),(178, 422),(152, 77),(126, 431)],
    (396, 168): [(178, 422),(164, 108),(126, 431),(152, 77)],
    (288, 235): [(178, 422),(126, 431),(152, 77),(164, 108)],
    (88, 248): [(164, 108),(178, 422),(152, 77),(126, 431)],
    }
    if isolated in preference_list_isolated:
        result = preference_list_isolated[isolated]
    return result

def begin_matching(isolated):
    preference_list_isolated = show_preference_list_isolated(isolated)
    print(preference_list_isolated)
    for relay in preference_list_isolated:
....

unboundlocalerror local variable 'result' referenced before assignment — user3356423, Nov 07 '17 at 04:24
Indentation matters in python. because `result` is indented within the `if` block, that's its scope. Only that. So on the next line (not indented) `result` is not in scope. Ergo, you're referencing a variable before it's been instantiated. — David Zemens, Nov 07 '17 at 04:29

Kaushik NP · Accepted Answer · 2017-11-07T04:36:51.223

In your code, the problem lies in the section :

if isolated in preference_list_isolated:
    result = preference_list_isolated[isolated]
return result

As Julien pointed out, what happens when isolated is not found in preference_list_isolated ? At that point it never enters the if loop, and since result = ... is never executed, there is no assignment to result. So when you try returning result, it will throw up an Error as at that point it would not be defined at all.

So, to rectify that, your one option maybe to assign it with a placeholder None before the if loop, like so :

result = None
if isolated in preference_list_isolated:
    result = preference_list_isolated[isolated]
return result

Or, put the return statement in the if loop, like so:

if isolated in preference_list_isolated:
    result = preference_list_isolated[isolated]
    return result

unboundlocalerror local variable 'result' referenced before assignment

1 Answers1