Find multiple list items within a string

Question

Working on a problem in which I am trying to get a count of the number of vowels in a string. I wrote the following code:

def vowel_count(s):
    count = 0
    for i in s:
        if i == 'a' or i == 'e' or i == 'i' or i == 'o' or i == 'u':
            count += 1
    print count
vowel_count(s)

While the above works, I would like to know how to do this more simply by creating a list of all vowels, then looping my If statement through that, instead of multiple boolean checks. I'm sure there's an even more elegant way to do this with import modules, but interested in this type of solution.

Relative noob...appreciate the help.

a way to do this: http://stackoverflow.com/questions/2926383/counting-vowels — Casimir et Hippolyte, Feb 26 '14 at 17:10
For learning's sake, if you want to maintain your current for loop structure, change the multiple boolean checks to `if i in ('a','e','i','o','u'):` — jayelm, Feb 26 '14 at 17:13
@JesseMu `if i in ('a', 'e', 'i', 'o', 'u'):` is more appropriate, because `if i in 'aeiou':` will also match `i == 'eio'`, which is not the intent of the code. — SethMMorton, Feb 26 '14 at 17:14

C.B. · Answer 1 · 2014-02-26T17:23:06.183

4

You can actually treat a string similarly to how you would a list in python (as they are both iterables), for example

vowels = 'aeiou'
sum(1 for i in s if i.lower() in vowels)

For completeness sake, others suggest vowels = set('aeiou') to allow not matching checks such as 'eio' in vowels. However note if you are iterating over your string in a for loop one character at a time, you won't run into this problem.

edited Feb 26 '14 at 17:23

answered Feb 26 '14 at 17:09

C.B.

8,096
5
20
34

3

`a string as a list` not exactly. both strings and lists are `iterables`, which allow them to but iterated. – njzk2 Feb 26 '14 at 17:12
`sum([i.lower() in vowels for i in s])` would also work because `True == 1` in python. – SethMMorton Feb 26 '14 at 17:16
@SethMMorton agreed more idiomatic. Since this is provided in Ashwini's post I'll leave as is. – C.B. Feb 26 '14 at 17:19
The proper syntax is either `set(['a','e','i','o','u'])` or `set('aeiou')` because `set` must take an iterable. – SethMMorton Feb 26 '14 at 17:23
@SethMMorton just fixed before your comment. – C.B. Feb 26 '14 at 17:23

score 4 · Accepted Answer · answered Feb 26 '14 at 17:10

4

No need to create a list, you can use a string like 'aeiou' to do this:

>>> vowels = 'aeiou'
>>> s = 'fooBArSpaM'
>>> sum(c.lower() in vowels for c in s)
4

answered Feb 26 '14 at 17:10

Ashwini Chaudhary

244,495
58
464
504

For ultimate speed and clarity, I would recommend `vowels = set('aeiou')`. This has two advantages: 1) Internally, this becomes `{'a', 'e', 'i', 'o', 'u'}` which is actually the intent of the code since `i in 'aeiou'` could match 'eou` and that is not what the OP wants, and 2) `set` memberships are fast (not really an issue here because the iterable is 5 elements but it could matter for longer strings). – SethMMorton Feb 26 '14 at 17:19

score 1 · Answer 3 · edited May 23 '17 at 12:10

A weird way around this is the following:

vowels = len(s) - len(s.translate(None, 'aeiou'))

What you are doing with s.translate(None, 'aeiou') is creating a copy of the string removing all vowels. And then checking how the length differed.

Special note: the way I'm using it is even part of the official documentation

What is a vowel?

Note, though, that method presented here only replaces exactly the characters present in the second parameter of the translate string method. In particular, this means that it will not replace uppercase versions characters, let alone accented ones (like áèïôǔ).

Uppercase vowels

Solving the uppercase ones is kind of easy, just do the replacemente on a copy of the string that has been converted to lowercase:

vowels = len(s) - len(s.lower().translate(None, 'aeiou'))

Accented vowels

This one is a little bit more convoluted, but thanks to this other SO question we know the best way to do it. The resulting code would be:

from unicodedate import normalize

# translate special characters to unaccented versions
normalized_str = normalize('NFD', s).encode('ascii', 'ignore')
vowels = len(s) - len(normalized_str.lower().translate(None, 'aeiou'))

-1 `strip` only removes trailing and leading characters. `s.translate(None, 'aeiou')` is an option though. — Ashwini Chaudhary, Feb 26 '14 at 17:13
Duh, my bad. I was checking the string methods and meant to use translate instead of split but my brain messed it up. Corrected — Toote, Feb 26 '14 at 17:14

score 0 · Answer 4 · answered Feb 26 '14 at 17:10

0

You can filter using a list comprehension, like so:

len([letter for letter in s if letter in 'aeiou'])

answered Feb 26 '14 at 17:10

njzk2

38,969
7
69
107

Find multiple list items within a string

4 Answers4

What is a vowel?

Uppercase vowels

Accented vowels