How to Use maketrans and translate in Python

In Python, use str.maketrans() to create a translation table that maps characters to their replacements, and then apply it with str.translate() to transform the string. This combination lets you replace, delete, or map characters efficiently in one step.

Syntax

str.maketrans() creates a translation table for character replacements. It can take three arguments: x and y are strings of equal length where each character in x is replaced by the character at the same position in y. The optional third argument is a string of characters to delete.

str.translate() applies this translation table to a string, returning a new string with replacements and deletions done.

python

table = str.maketrans(x, y, z)
new_string = original_string.translate(table)

Example

This example replaces vowels with numbers and removes punctuation from the string.

python

text = "Hello, World!"
# Replace vowels: a->1, e->2, i->3, o->4, u->5
# Remove punctuation: , and !
translation_table = str.maketrans("aeiou", "12345", ",!")
result = text.translate(translation_table)
print(result)

Output

H2ll4 W4rld

Common Pitfalls

• Passing strings of different lengths to maketrans() for x and y causes a ValueError.
• For deleting characters, only provide them in the third argument; do not include them in x or y.
• Remember translate() returns a new string; it does not change the original string.

python

try:
    # Wrong: different lengths for x and y
    table = str.maketrans("abc", "de")
except ValueError as e:
    print(f"Error: {e}")

# Correct usage
table = str.maketrans("abc", "def")
print("abcabc".translate(table))

Output

Error: the first two maketrans arguments must have equal length

defdef

Quick Reference

str.maketrans(x, y, z)

• x: string of characters to replace
• y: string of replacement characters (same length as x)
• z: string of characters to delete

str.translate(table) applies the translation table to a string.

Function	Purpose
str.maketrans(x, y, z)	Create translation table for replacements and deletions
str.translate(table)	Apply translation table to string

Key Takeaways

Use str.maketrans() to create a mapping table for character replacements and deletions.

Apply the translation table with str.translate() to get the transformed string.

Ensure the first two arguments to maketrans() are strings of equal length.

Characters to delete go only in the third argument of maketrans().

translate() returns a new string; it does not modify the original.