Unusual behaviour when using string concatenation inside for loop

Question

So the code below properly removes all the vowels from a string as expected.

def disemvowel(string):
    # Letters to remove & the new, vowerl free string
    vowels_L = list('aeiouAEIOU')
    new_string = ""

    # Go through each word in the string
    for word in string:

        # Go through each character in the word
        for character in word:

            # Skip over vowels, include everything elses
            if character in vowels_L:
                pass
            else:
                new_string += character

    # Put a space after every word
    new_string += ' '

    # Exclude space place at end of string
    return new_string[:-1]

no_vowels = disemvowel('Nasty Comment: Stack exchange sucks!')
print(no_vowels)

>>>>python remove_vowels.py
>>>>Nsty Cmmnt: Stck xchng scks!

However, when I move the statement: "new_string+= ' '" to where I think it should be (I come from a C/C++ background), I end up getting a weird answer,

def disemvowel(string):
    # Letters to remove & the new, vowerl free string
    vowels_L = list('aeiouAEIOU')
    new_string = ""

    # Go through each word in the string
    for word in string:

        # Go through each character in the word
        for character in word:

            # Skip over vowels, include everything elses
            if character in vowels_L:
                pass
            else:
                new_string += character

    # THIS IS THE LINE OF CODE THAT WAS MOVED        
    # Put a space after every word
    new_string += ' '

    # Exclude space place at end of string
    return new_string[:-1]

no_vowels = disemvowel('Nasty Comment: Stack exchange sucks!')
print(no_vowels)

>>>>python remove_vowels.py
>>>>N  s t y   C  m m  n t :   S t  c k    x c h  n g    s  c k s !

Instead of placing a space after a word has finished being iterated over exclusively, a space is also place wherever there was a vowel. I was hoping someone would be able to explain why this occurs, even though in C the result would be quite different. Also, any suggestions to streamline/condense the could would be welcome! : )

Your code isn't indented properly here, which makes it impossible to analyze without making guesses about how it's actually indented. — interjay
– interjay, Commented Apr 11, 2015 at 22:07
@martineau: Please don't fix problems in the original question. It makes nonsense of the solutions that explain how to correct the code — Borodin
– Borodin, Commented Apr 11, 2015 at 22:31

user2357112 · Accepted Answer · 2015-04-11 22:07:16Z

8

for word in string doesn't iterate over the words; it iterates over the characters. You don't need to add spaces at all, because the spaces in the original string are preserved.

answered Apr 11, 2015 at 22:07

user2357112

286k32 gold badges490 silver badges570 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Aiden Over a year ago

Oh, that makes a total sense! Thanks for the explanation.

Borodin Over a year ago

There is much more wrong with the OP's code than that!

user2357112 Over a year ago

@Borodin: There is, but it looks like mostly awkward ways of doing things or formatting errors introduced when the code was copied into the question. The indentation problems look exactly like what you'd get if you hit the code button and then pasted your code where the message tells you to put it.

Borodin Over a year ago

@user2357112: Maybe, but I can't reproduce what you describe. Do you mean the Code snippet button, Ctrl/M? That's for JavaScript and makes something completely different. Or the Code sample button, Ctrl/K? That adds an extra four-space indent to the first line, but otherwise seems okay. Can you explain please?

user2357112 Over a year ago

@Borodin: The one with the braces. If you hit that button and then paste in code, only the first line gets the extra 4 spaces it needs, and everything after that comes out insufficiently indented. It's a long-standing problem that confuses new users again and again, and it's particularly annoying for Python questions, where indentation is crucial.

|

Community · Accepted Answer · 2017-05-23 10:24:18Z

0

As interjay comments, your indentation is way out. Python relies on the indentation to describe which statements belong to what block, instead of the more common BEGIN ... END or { ... }.

In addition, user2357112 observes that you are expecting words from your string, whereas a string is simply a list of characters, and for word in string will set word to one character of string at a time

It is also much cleaner to use not in rather than an if together with a pass.

This is much closer to what you intended

def disemvowel(string):

    # Letters to remove & the new, vowel-free string
    vowels_list = 'aeiouAEIOU'
    new_string = ""

    # Go through each character in the string
    for character in string:

        # Skip over vowels, include everything else
        if character not in vowels_list:
            new_string += character

    return new_string


print disemvowel('Nasty Comment: Stack exchange sucks!')

output

Nsty Cmmnt: Stck xchng scks!

edited May 23, 2017 at 10:24

CommunityBot

11 silver badge

answered Apr 11, 2015 at 22:28

Borodin

127k9 gold badges72 silver badges146 bronze badges

1 Comment

Aiden Over a year ago

Yeah, I don't know why I thought typing 'word' would magically make python appropriately parse the string for me. Thanks for the tip about "not in", and refining the code I posted; pointing out the differences between good and bad code definitely helps me learn the language more quickly, so thank you!

Collectives™ on Stack Overflow

Unusual behaviour when using string concatenation inside for loop

2 Answers 2

6 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related