Python good programming practice for enumerating lists

Question

I'm pretty new to Python and programming in general, and I was wondering if it is a good programming practice to write long statements with many logic operators - for example, in a for loop.

For example, here's a function I made that gets all the vowels from a word and returns a list containing those vowels.

def getVowels(word):
    vowel_list = []
    index = 0
    for i in word:
        if i == "a" or i == "e" or i == "i" or i == "o" or i == "u" or i == "A" or i == "E" or i == "I" or i == "O" or i == "U":
            vowel_list.append(word[index])
        index += 1
    return vowel_list

As you can see, the if statement has gotten very long. Is it considered good programming? If it's not, is there a better way to code this function?

Answer 1

No it is not considered good practice, there are always better ways :D

if i.upper() in "AEIOU"

Here is a much shorter version of your function using list comprehensions:

def get_vowels(word):
    vowels = "AEIOU"
    return [c for c in word if c.upper() in vowels]

Answer 2

Would probably be better to use sets:

VOWELS = set('aeiouAUIOU')

def get_vowels(word):
    return [c for c in word if c in VOWELS]

or, more geeky:

def get_vowels(word):
    return filter(VOWELS.__contains__, word)

(But the first approach is most readable and as such is more pythonic. Also, the second function will return generator, not a list in Python 3.)

EDIT performance comparison of c in list vs c in set:

import timeit

VOWELS = 'aeiouAEIOU'
VOWSET = set(VOWELS)
SAMPLE = 'asflasrjoperugASDFAROUAoarfpeoriugargagadropgue'

def get_vowels(word, vowels):
    return [c for c in word if c in vowels]

print timeit.timeit('get_vowels(SAMPLE, VOWELS)', 
                    'from __main__ import VOWELS, SAMPLE, get_vowels') 
# ^ prints 10.0739870071
print timeit.timeit('get_vowels(SAMPLE, VOWSET)', 
                    'from __main__ import VOWSET, SAMPLE, get_vowels') 
# ^ prints 9.43965697289