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Hello Python

Count Vowels

Practice ExerciseBeginnerEasyStringLinear Search

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Problem

Implement count_vowels(text). Return how many characters are a, e, i, o, or u, ignoring case.

Starter code

def count_vowels(text):
    pass
Test cases

mixed-case

{
  "args": [
    "OpenAI"
  ]
}

Expected: 4

Wizard outline
  1. Step 1: Count lowercase vowel membership

    Translate the vowel definition into a direct membership predicate. The counting expression should encode exactly five accepted letters before case normalization is added.

  2. Step 2: Normalize case per character

    Count uppercase and lowercase vowels identically. Lowercasing each character preserves the scan while making membership case-insensitive.

Footguns and prerequisites
  • Uppercase vowels must count too.
  • strings
Reviewed references
Recommended approach and implementation

Lowercase each character and count membership in the five-vowel set.

Why it works: The scan adds one exactly for each case-normalized vowel and zero for every other character.

def count_vowels(text):
    return sum(character.lower() in 'aeiou' for character in text)
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