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Python Python Collections (2016, retired 2019) Lists Disemvowel

Posted by Bozhong Tao
Bozhong Tao
18,365 Points

Why is my code not returning the right outcome?(always miss a letter)

Hi , thanks for checking up on my code :)

my logic is:

  1. turn the word into a list

  2. for every letter in the word, compare it to every vowel in the vowels list (vowels = ['a', 'e', 'i', 'o', 'u'])

  3. I will compare both the upper case of vowels and lower case(them-self)

  4. if the letter matches(no matter lower case or upper case), remove it from the word. start from the next letter in word

  5. then join the processed list back into a string and return as the word

Somehow I always miss a vowel, I don't know what caused this, some help would be really appreciated!

disemvowel.py 
def disemvowel(word):
    vowels = ['a', 'e', 'i', 'o', 'u']

    word = list(word)

    for letter in word:
        for vow in vowels:    
            if vow.upper() == letter or vow == letter:
                word.remove(letter)                

    word = ''.join(word)
    return word

3 Answers

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

This is a common issue and it's a result of modifying an iterator inside the loop that it is controlling. It causes elements to be skipped in the loop.

One easy remedy is to use a copy of the list as the iterator for the loop.

Bozhong Tao
Bozhong Tao
18,365 Points
Bozhong Tao
Bozhong Tao
18,365 Points

I see, so when the loop modify the word list on the go, it will change the index of the letter which will cause the skip issue right? That make sense!

Thanks again @stevenparker !! :D

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

You got it. And if you were adding to the list it could cause the loop to repeat items.

Bozhong Tao
Bozhong Tao
18,365 Points
Bozhong Tao
Bozhong Tao
18,365 Points

Thanks for the extra tip. One less mine for me to step on in future codes! Cheers Steven :)

PS. this might be useful for anyone who has similar issues and try to 'copy' the list for iteration - https://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list