Why does this code print out only the first letter?

Question

Word=input('please enter a word')
def cap(word):
      for char in word:
            if char in 'aeiou':
                  return letter.upper()

            else:
                  return letter

result=cap(word)
print result

Because you can only return from a given function invocation once. — jonrsharpe, Jul 07 '19 at 20:58
Build a single result to return. Also I'd suggest upgrading to Python 3. — jonrsharpe, Jul 07 '19 at 20:59
Collect the letters in a list or append to string and finally (after the loop) return that. — Michael Butscher, Jul 07 '19 at 21:00
I use python 3. Here is the question: Build a function to capitalize every vowel in a string — Flahmez, Jul 07 '19 at 21:00
Along with the main issue, you're iteration variable is `char` but you're returning `letter`. Also `Word != word` — Mark, Jul 07 '19 at 21:01

score 3 · Answer 1 · answered Jul 07 '19 at 21:02

You return immediately after examining the first character. Instead, you should go over all of them, and modify the ones you need.

def cap(word):
    result = ''
    for letter in word:
        if letter in 'aeiou':
            result += letter.upper()
        else:
            result += letter
    return result

Note, however, that this may be much easier to do with list comprehensions:

def cap(word):
    return ''.join(l.upper() if l in 'aeiou' else l for l in word)

score 0 · Accepted Answer · answered Jul 07 '19 at 21:11

In python you can have functions that continuously return values — they're called generators. You just use yield instead of return. You can then use them as iterators, or call list on them to get the values:

word=input('please enter a word')
def cap(word):
      for letter in word:
            if letter in 'aeiou':
                  yield letter.upper()

            else:
                  yield letter

result=cap(word)
print(''.join(list(result)))

However, if your goal is to translate a set of characters to another set of characters, there is a python string method for that: translate().

word=input('please enter a word')
upper_vowels = word.translate(str.maketrans('aeiou', 'AEIOU'))

print(upper_vowels)

This should be more efficient that looping and joining as well being easier to read. Also, you can save the translate table separately if you want to apply it to many strings.

Why does this code print out only the first letter?

2 Answers2