I can't understand! My code is working but not up to the end.

Question

It works actually, but in a very strange way, it prints 'trhuse' at the end. Why the letter 'u' is not deleted? And I've noticed that it happens to all long words. The function deleting only first 3 letters. But when I enter, for instance 'banana', with several repeated letters, it works perfect.

def disemvowel(word):
    vowels = ['a',  'e',  'i',  'o', 'u']
    word = list(word)
    print(word)
    for letter in word:
        if letter.upper().lower() in vowels:
            word.remove(letter)
    word= ''.join(word)       
    print(word)
disemvowel("trEehouse")

Answer 1 · 2017-06-13T21:24:00Z

June 13, 2017 9:24pm

A common error is modifying the container being iterated over by the for loop. By using word.remove() it changes the indexing of the items within word thus effectively skipping a index.

Adding a print statement shows the errant flow:

>>> def disemvowel(word):
...     vowels = ['a',  'e',  'i',  'o', 'u']
...     word = list(word)
...     print(word)
...     for letter in word:
...         print("letter", letter)
...         if letter.upper().lower() in vowels:
...             word.remove(letter)
...     word= ''.join(word)
...     print(word)
...
>>> disemvowel("trEehouse")
['t', 'r', 'E', 'e', 'h', 'o', 'u', 's', 'e']
letter t
letter r
letter E
letter h
letter o
letter s
letter e
trhuse

The first lower case e is skipped due the the remove of E. The u is skipped due to the removal of the o, and the final e causes the originally skipped e to be remove due to the "first match" found by remove().

The solution is to use a copy of word in the iteration so that removals from the actual word does not effect the flow. This can be easily done by adding the slice notation: "[:]"

>>> def disemvowel(word):
...     vowels = ['a',  'e',  'i',  'o', 'u']
...     word = list(word)
...     print(word)
...     for letter in word[:]:  # <-- added slice notation
...         print("letter", letter)
...         if letter.upper().lower() in vowels:
...             word.remove(letter)
...     word= ''.join(word)
...     print(word)
...
>>> disemvowel("trEehouse")
['t', 'r', 'E', 'e', 'h', 'o', 'u', 's', 'e']
letter t
letter r
letter E
letter e
letter h
letter o
letter u
letter s
letter e
trhs

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Nikolay Nogin

Nikolay Nogin

I can't understand! My code is working but not up to the end.

1 Answer

Chris Freeman

Chris Freeman

Nikolay Nogin

Nikolay Nogin