updating python list on recurison call returns None

Question

def get_name():
    import random
    lst = ["aa", "bbb", "ccc", "dddd", "eee", "stop"]
    return random.choice(lst)

def poi(name, lst):
    res = get_name()
    lst.append(res)
    if res !="stop":
        poi(name, lst)
    else:
        print lst
        return lst


if __name__ == '__main__':
    print poi("xx", [])

poi() method add items in a passed list and should return list until "stop" is in the list. If "stop" is in the list then returns the list

print lst prints ['bbb', 'dddd', 'bbb', 'stop'] #1

But

`print poi("xx", [])` prints `None`  #2

Why #2 is printing None instead of updated list ?

Or e.g. http://stackoverflow.com/q/2599149/3001761, or http://stackoverflow.com/q/15210646/3001761 — jonrsharpe, Jan 06 '15 at 12:22

score 2 · Accepted Answer · answered Jan 06 '15 at 12:14

2

The

poi(name, lst)

should be

return poi(name, lst)

Without the return statement, the function is implicitly returning None.

answered Jan 06 '15 at 12:14

NPE

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updating python list on recurison call returns None

1 Answers1