Getting a RecursionError: maximum recursion depth exceeded while calling a Python object when running my flask app

Question

I'm trying to loop through a list of values I got from database

I tried using a while loop to go through it while less than a number of times given by the user.

def winner(x):
    winner = random.choice(x)
    return winner_list(x, winner)

winner_lists = []
def winner_list(y, x):
    if x not in winner_lists:
        winner_lists.append(x)
    else:
        winner(y)

i = 0
competitors = User.query.all() #gotten from database
main_competitors = []
for competitor in competitors:
    competitor_raffles = competitor.raffles.split(',')
    if uuid in competitor_raffles:
        main_competitors.append(competitor.uuid.strip(' '))
while (i < form.number.data) and (main_competitors != []):
    winner(main_competitors)
    i+=1

I expect to see randomly chosen names from the list competitors

I honestly understand what you mean because I just reviewed the code now, but I really do not know how to apply a fix because it is meant to stop iterating once 'i' is equal to the user input — Metete-Welete
– Metete-Welete, Commented Jun 6, 2019 at 2:08
why do you think you need recursion for this? You have a known maximum number of function calls. just pop the winner from the competitors list and forget recursion here. — David Zemens
– David Zemens, Commented Jun 6, 2019 at 2:09
K-K -- i never > 0 in your code. The recursion fails before i+=1. — David Zemens
– David Zemens, Commented Jun 6, 2019 at 2:10
I understand you and I tweaked it. I didn't need the functions after all. I worked with an if statement inside the while block. Thank you very much — Metete-Welete
– Metete-Welete, Commented Jun 6, 2019 at 2:18

Eric Zhou · Accepted Answer · 2019-06-06 02:08:27Z

1

It looks like the problem is in the while loop. When winner_lists has all of the main_competitors in it, then the functions winner and winner_lists keep calling each other since it is impossible to choose a new winner.

Maybe you forgot to remove a competitor from main_competitors each time winner is run.

answered Jun 6, 2019 at 2:08

Eric Zhou

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David Zemens · Accepted Answer · 2019-06-06 02:27:45Z

winner_list doesn't return a value to the caller. There's a bit to unpack here including the fact that you're using variable names that shadow your function names, among other things I'd change, but ultimately this is not a problem that requires recursion.

Why not? You know how many times to maximally choose a winner (from form.number.data), and you have a list of competitors of certain length.

This example chooses only unique winners. If a competitor can "win" more than once, then just remove the last line.

results = []
how_many_winners = form.number_data
contestants = main_competitors[:]
while main_competitors and len(results) < how_many_winners:
    this_winner = random.choice(contestants)
    results.append(this_winner)
    contestants.remove(this_winner)   # Remove this line if a contestant can 'win' more than once

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