Python - Replace vowels in a string with a specific character K

The task is to replace all the vowels (a, e, i, o, u) in a given string with the character 'K'. A vowel can be in uppercase or lowercase, so it's essential to account for both cases when replacing characters.

Using str.replace() in a Loop

Using str.replace() in a loop allows us to iteratively replace specific substrings within a string. This method is used when we need to perform multiple replacements or when the substrings to be replaced vary based on certain conditions during the loop.

# Input string
s = "hello world"
# Define the vowels and the replacement character
v = "aeiouAEIOU"
r = "K"
# Replace each vowel with the replacement character
for vowel in v:
    s = s.replace(vowel, r)
# Print the result
print(s)

hKllK wKrld

Explanation

• loop iterates over each vowel in the string v, and in each iteration, str.replace() replaces all occurrences of that vowel in the string s with the character r.
• After processing all the vowels, the string "hello world" becomes "hKllK wKrld", and the result is printed.

Let's explore various other methods to Replace vowels in a string with a specific character K.

Using List Comprehension

Using list comprehension allows you to efficiently iterate through a string and apply a transformation, such as replacing characters, while creating a new list. This method is concise and often more readable than using a loop with replace().

# Input string
s = "hello world"
# Define the vowels and the replacement character
v = "aeiouAEIOU"
r = "K"
# Replace vowels with the replacement character using list comprehension
result = ''.join([r if char in v else char for char in s])
# Print the result
print(result)

hKllK wKrld

Explanation

• list comprehension iterates through each character in the string s. If the character is a vowel (i.e., it exists in v), it is replaced with r. Otherwise, the character remains unchanged.
• After joining the modified characters into a new string, the result is "hKllK wKrld", and it is printed.

Using re.sub()

Using re.sub() with regular expressions allows you to replace all occurrences of a pattern in a string.

import re
# Input string
s = "hello world"
# Define the vowels and the replacement character
v = "aeiouAEIOU"
r = "K"
# Use regex to replace vowels with the replacement character
result = re.sub(r'[aeiouAEIOU]', r, s)
# Print the result
print(result)

hKllK wKrld

Explanation

• The re.sub() function uses a regular expression pattern r'[aeiouAEIOU]' to match any character that is a vowel (both lowercase and uppercase). It then replaces each match with the character r.
• The string "hello world" is transformed into "hKllK wKrld", and the result is printed.