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Python Python Collections (2016, retired 2019) Lists Disemvowel

Posted by Alfonso Lopez
Alfonso Lopez
6,089 Points

Disemvowel: Uncertain why solution does not receive a pass.

I have tested the following in an iPython notebook and appears to work in different test cases for a single word. Can anyone tell me why the solution does not pass the requirement of removing all vowels from a given work (tested for upper and lower case).

disemvowel.py 
def disemvowel(word):
    word = list(word)
    vowels = ["a", "e", "i", "o", "u", 'A', 'E', 'I', 'O', 'U']
    x = True
    for letter in word:
        if letter in vowels:
            while x == True:
                try:
                    word.remove(letter)
                except:
                    break
        else:
            continue
    word = ''.join(word)
    return word

2 Answers

Christopher Shaw
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Christopher Shaw
Python Web Development Techdegree Graduate 58,248 Points
Christopher Shaw
.a{fill-rule:evenodd;}techdegree seal-36
Christopher Shaw
Python Web Development Techdegree Graduate 58,248 Points

Unfortunately, you have to rethink your answer.

Test it with:

disemvowel('aeiouAEIOU')

and you will get back 'eoAIU'.

This is because, as it removes the first 'a', the list shifts left, so the next item is not 'e' as you are expecting, but 'i'.

Rather than iterate the word, iterate the vowels, then use word.remove(vowel) and this will remove all instances of that vowel from the word. Also, there is no need for the try, as there will be no exception if no letter is removed.

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

But doesn't remove act only on the first instance of a term?

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

I bet you didn't test it on a word like "boat". :smirk:

When you iterate on a sequence, and then modify the same sequence inside the loop, you can cause unexpected behavior such as having items skipped over.

Two ways to avoid this are to iterate on a copy of the sequence, or instead of modifying it in the loop, construct a new result instead.

Also, you dont need "x". You can just say "while True:".

Alfonso Lopez
Alfonso Lopez
6,089 Points

Thanks, I'll remember that for the while loop.

Here it is for "balloon": https://screencast.com/t/fOeMeACKch

You can see the result in the lower-left hand corner. It appears to work for this. However, "eoAIU" does return "oI" so I will investigate further.

Thanks again for the help!

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

I changed my example word to "boat", I had suggested "baloon" without trying it first myself. But the principle is correct.

The quickest fix might be to use a slice to make a copy of the iterable:

    for letter in word[:]: