Python String maketrans() Method

The maketrans() method is a built-in function used to create a translation table. This table can then be used with the translate() method to replace specified characters in a string with new characters.

Syntax

str.maketrans(x, y, z)

Parameters:

• x: A dictionary or a string containing characters to be replaced
• y: A string with characters to replace x (must be the same length)
• z: (Optional) A string of characters to be removed

Returns:

• A translation table that can be used with str.translate()

Example 1: Replace Characters Using maketrans()

table = str.maketrans("aeiou", "12345")
text = "hello world"
translated = text.translate(table)
print(translated)

h2ll4 w4rld

Example 2: Remove Characters Using maketrans()

table = str.maketrans("", "", "aeiou")
text = "hello world"
translated = text.translate(table)
print(translated)

hll wrld

Example 3: Use Dictionary in maketrans()

table = str.maketrans({97: 49, 98: 50})  # a → 1, b → 2
text = "abc"
print(text.translate(table))

12c

Use Case: Why Use maketrans()?

• Efficient way to substitute multiple characters at once
• Used in text preprocessing, encryption, and formatting
• Combines cleanly with translate() for powerful string manipulation

Common Mistakes

• Mismatch Length: If x and y are strings, they must be of equal length.
• Wrong Type: Don't forget to call translate() on the actual string—not on the translation table.

Interview Tip

In coding rounds, maketrans() + translate() is often used for character substitution problems like encoding, sanitizing input, or removing unwanted characters.

Summary

• maketrans() creates a translation table
• Used with translate() to modify strings
• Supports string mapping and character removal

Practice Problem

Write a program that replaces all vowels in user input with * using maketrans().

text = input("Enter some text: ")
table = str.maketrans("aeiouAEIOU", "**********")
print(text.translate(table))