Python - Replace all numbers by K in given String

We need to write a python program to replace all numeric digits (0-9) in a given string with the character 'K', while keeping all non-numeric characters unchanged.
For example we are given a string s="hello123world456" we need to replace all numbers by K in the given string so the string becomes "helloKKKworldKKK".

Using str.translate with a Translation Table

str.translate() method in Python allows for replacing multiple characters in a string using a translation table. A translation table is typically created with str.maketrans(), which maps characters to their replacements.

s = "hello123world456"

# Replacing digits with 'K' using translate and maketrans
res = s.translate(str.maketrans("0123456789", "K" * 10))


print(res)

helloKKKworldKKK

Explanation:

• str.maketrans creates a translation table mapping digits (0-9) to the letter K.
• Translate applies the translation to the string.

Using Regular Expressions (re.sub)

re.sub() method in Python allows for replacing parts of a string that match a regular expression pattern. It takes the pattern, the replacement string, and the original string as arguments.

import re
s = "hello123world456"

# Replacing digits (\d) with 'K' using re.sub
res = re.sub(r'\d', 'K', s)

print(res)

helloKKKworldKKK

Explanation:

• Regex pattern \d matches any digit in the string.
• re.sub replaces each digit with K.

Using List Comprehension

Using list comprehension with string manipulation allows us to create a new list by applying an operation to each character or substring in a string.

s = "hello123world456"

# Replacing digits with 'K' using list comprehension
res = ''.join(['K' if char.isdigit() else char for char in s])

print(res)  

helloKKKworldKKK

Explanation:

• List comprehension iterates through each character in the string.
• If the character is a digit (char.isdigit()), it’s replaced with K; otherwise, it remains unchanged.