'Nonetype' error in middle of function (Python 3.6)

Asked May 25 '20 at 00:59

Active Sep 14 '22 at 15:04

Viewed 27 times

def letters_to_words():
        d = {}
        wordlist = read_file(file)
        for word in wordlist:
                key = tuple(sorted(word))
                val = d.get(key, [])
                d[key] = val.append(word)
        return d

Please note that wordlist is a list of words. I don't understand why the penultimate line of this function raises "AttributeError: 'NoneType' object has no attribute 'append'. Here, val equals the return of the .get method, which shouldn't be returning None since a second argument is provided.

When I add print(type(val)) below the problematic line, every iteration returns except the last, which returns

Note: I've been able to bypass this error by using + instead of the .get method, but would really like to understand this problem.

Thanks for any help in advance.

asked May 25 '20 at 00:59

Alex Yuwen

5

`list.append()` returns `None`. You need `val.append(word) d[key] = val` – Nick May 25 '20 at 01:04
@Nick Would you mind writing this up in an answer? – jacob May 25 '20 at 01:06
Does this answer your question? [Python function returns None, unclear why](https://stackoverflow.com/questions/10459673/python-function-returns-none-unclear-why) – Preston Hager May 25 '20 at 01:08
@jacob it's a duplicate, see the one I proposed – Nick May 25 '20 at 01:10

'Nonetype' error in middle of function (Python 3.6)

0 Answers0