How can I only return words that contain specified letters?

Question

The title ^. For some reason the code I have now is allowing words to slip through that evidently don't contain the required letters.

listOfValid = ["xxxxy", "xxxxz", "xxxxx", "a", "ab"]
lettersIn = ["a", "b"]

for word in listOfValid:
    for letter in lettersIn:
        if letter not in word and word in listOfValid:
            listOfValid.remove(word)

print(listOfValid)

This returns: 'xxxxz' 'a' 'ab'. Why is it allowing xxxxz and a through?

Why are you checking `and word in listOfValid:` ? you take `word`from this list! — Patrick Artner, Feb 14 '22 at 12:57
Why do you iterate a list and modify it. That is a big NO-NO. — Patrick Artner, Feb 14 '22 at 12:58
That might be because you're modifying the list that you're iterating through. Try creating a new empty list and use `append` to add values to the new list. Also you'll have to change your condition to the opposite (`letter in word`) — aaossa, Feb 14 '22 at 12:58

score 1 · Answer 1 · answered Feb 14 '22 at 13:01

Perhaps you wanted to do this?

listOfValid = ["xxxxy", "xxxxz", "xxxxx", "a", "ab"]
lettersIn = ["a", "b"]

for word in listOfValid[:]:
    for letter in lettersIn:
        if letter in word:
            break
    else:
        listOfValid.remove(word)

print(listOfValid)

Try it online!

You can't iterate on an array that you are modifying, so listOfValid[:] copies the array.

Although you should probably do something more like this:

listOfValid = ["xxxxy", "xxxxz", "xxxxx", "a", "ab"]
lettersIn = ["a", "b"]

listOfValid = [*filter(lambda i:any(map(lambda l:l in i,lettersIn)),listOfValid)]

print(listOfValid)

Try it online!

score 1 · Answer 2 · answered Feb 14 '22 at 13:13

1

Using list compreenssion this should work:

[x for x in listOfValid if x in lettersIn]

answered Feb 14 '22 at 13:13

Franz Kurt

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How can I only return words that contain specified letters?

2 Answers2