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Python Python Collections (2016, retired 2019) Lists Disemvowel

Kayla Johhnson
Kayla Johhnson
756 Points


Ok, so i finally figured this out for the most part. For one, I was confusing the methods .upper and .lower = I figured you use upper (when you have provided lower case vowels) to catch any upper case vowels passed through. But actually you use .lower (if you have, indeed provided lower case vowels in your list of vowels) to coerce any letters passed through to lower case so that they are caught.

I needed to communicate that so that it will sink in.

What I don't get: when you use the For Loop why do you need to use a copy of the list or the word itself versus just using the list form of the word?

Why do these work:

for letter in letters.copy() for letter in word

But this doesn't:

for letter in letters

def disemvowel(word):
    vowels = ["a" , "e" , "i" , "o" , "u"] 
    letters = list(word)
    for letter in letters:
        if letter.lower() in vowels:
    word = "".join(letters)
    return word

1 Answer

Steven Parker
Steven Parker
224,848 Points

If you alter an interable while it is controlling a loop, you throw off the internal mechanisms of the loop and cause items to be skipped over.

But if you use a copy of the iterable to control the loop, you can make changes safely.