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Number of Vowels in a String

Certification: Basic Level Accuracy: 57.89% Submissions: 57 Points: 5

Write a Python program that counts the number of vowels (a, e, i, o, u) in a given string.

Example 1
    

  • Input: string = "Hello World"
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  • Output: 3
    • 

  • Explanation: 
      

    • Step 1: Initialize a counter variable to 0.
      • 

    • Step 2: Iterate through each character in the string.
      • 

    • Step 3: Check if each character is a vowel (a, e, i, o, u) in case-insensitive manner.
      • 

    • Step 4: The vowels in "Hello World" are 'e', 'o', 'o' (3 vowels).
      • 

    • Step 5: Return the count of vowels: 3.
      • 

    •
Example 2
    

  • Input: string = "Python"
    • 

  • Output: 1
    • 

  • Explanation: 
      

    • Step 1: Initialize a counter variable to 0.
      • 

    • Step 2: Iterate through each character in the string.
      • 

    • Step 3: Check if each character is a vowel (a, e, i, o, u) in case-insensitive manner.
      • 

    • Step 4: The only vowel in "Python" is 'o' (1 vowel).
      • 

    • Step 5: Return the count of vowels: 1.
      • 

    •
Constraints
    

  • 1 ≤ len(string) ≤ 10^6
    • 

  • The string may contain uppercase and lowercase letters.
    • 

  • The string contains printable ASCII characters.
    • 

  • Time Complexity: O(n), where n is the length of the string
    • 

  • Space Complexity: O(1), as it only uses a counter
    •
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Hint
Solution

The following are the steps to count the number of vowels in a string:


  • Iterate with a loop: Use a loop to check each character and count vowels.

  • Use list comprehension: sum(1 for char in s if char.lower() in "aeiou").

  • Use regular expressions: len(re.findall(r'[aeiouAEIOU]', s)).

  • Convert to lowercase: Convert the string to lowercase for easier comparison.

The following are the steps to count the number of vowels in a given string:

  • def count_vowels(input_string): Defines a function named count_vowels that takes a string input_string as input.
  • count = 0: Initializes a variable count to 0, storing the number of vowels found.
  • vowels = "aeiouAEIOU": Creates a string of vowels containing all lowercase and uppercase vowels.        
  • for char in input_string: Loops through each character (char) in the input string.
  • if char in vowels: Checks if the current character is present in the vowels string.
  • count += 1: If the character is a vowel, the count is incremented by 1.        
  • return count: After the loop finishes, the function returns the final value of count, which is the total number of vowels in the string.
  • The function count_vowels is called with "Hello World", and the result is saved in result.     
  • print(result): Prints the value of result to the console.
    •

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