Problem 8: Count Vowels

Source: Dev.to

Examples

count_vowels("hello world")  # → 3
count_vowels("AEIOU")        # → 5

Solution

def count_vowels(s):
    """
    Counts the number of vowels in a string.
    """
    vowels = {'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'}
    count = 0
    for char in s:
        if char in vowels:
            count += 1
    return count

# Test case
print(count_vowels("pooopcycle"))  # Output: 4

Walkthrough

• Function definition: def count_vowels(s): creates a function that accepts a string s.

• Vowel set: vowels = {...} stores all lowercase and uppercase vowels in a set for O(1) lookups.

• Counter initialization: count = 0 starts the vowel counter.

• Iteration: for char in s: loops through each character in the input string.

• Check & increment:

  if char in vowels:
      count += 1

  Increments count when the current character is a vowel.

• Return: return count provides the total number of vowels found.

Example trace for "pooopcycle"

The function correctly returns 4 for this input.

Happy coding! 💻