Python String translate() Method

Python translate() method is used to transform a string by replacing or removing specific characters based on a translation table. This table is created using the str.maketrans() method. It’s ideal for scenarios where we need to:

1. Replace specific characters with others.
2. Remove unwanted characters like punctuation, digits or whitespace.
3. Perform transformations without looping through the string manually.

Example:

In the given example, we are using str.translate() method is used to translate a string by specifying a mapping using ASCII values.

# Creating a translation table
tab = str.maketrans("aeiou", "12345")

# Original string
s = "hello world"

# Translating the string
res = s.translate(tab)
print(res)

h2ll4 w4rld

Let's explore python string translate() method in detail:

Syntax of translate() method:

str.translate(table)

Parameters:

• table: A translation table created using the str.maketrans() method.

Returns:

• A new string where the specified characters are replaced or removed according to the translation table.

Python maketrans()

The maketrans() method is a built-in string method in Python that generates a translation table. It is primarily used in conjunction with the translate() method to perform character-by-character translations or deletions.

Python maketrans() Syntax

Syntax: maketrans(str1, str2, str3) 

Parameters: 

• str1: Specifies the list of characters that need to be replaced. 
• str2: Specifies the list of characters with which the characters need to be replaced. 
• str3: Specifies the list of characters that need to be deleted.

Returns: Returns the translation table which specifies the conversions that can be used by translate()

Example 1: Removing Specific Characters with Translate

We can use translate() to remove unwanted characters, like punctuation. Removing punctuation from a string is a common task, especially in text preprocessing for Natural Language Processing (NLP) or data cleaning.

Example:

# Remove punctuation
import string

s = "Hello, World! Welcome to Python."
tab = str.maketrans("", "", string.punctuation)
res = s.translate(tab)
print(res)

Hello World Welcome to Python

Explanation:

• Translation Table: The str.maketrans("", "", string.punctuation) specifies no replacements but deletes all characters listed in string.punctuation. This includes characters like !, ., ,, and others.

Example 2: Replacing Multiple Characters

Replace multiple characters in a string using a custom mapping. In this example, we demonstrate how to map specific characters to others for custom transformations.

Example:

# Replace spaces with underscores and vowels with '*'
tab = str.maketrans({" ": "_", "a": "*", "e": "*", "i": "*", "o": "*", "u": "*"})
s = "This is an example."
res = s.translate(tab)
print(res)

Th*s_*s_*n_*x*mpl*.

Explanation:

• Replacement Rules: Replace spaces (' ') with underscores ('_'). Replace vowels ('a', 'e', 'i', 'o', 'u') with the '*' character.

Example 3: Building a Simple Cipher

Let’s build a basic substitution cipher using the translate() method. This is often used in simple encryption or encoding scenarios.

Example:

# Simple substitution cipher
tab1 = str.maketrans("abcdef", "uvwxyz")
s = "abcde fg"
encoded = s.translate(tab1)
print("Encoded:", encoded)

# Decoding the text
tab2 = str.maketrans("uvwxyz", "abcdef")
decoded = encoded.translate(tab2)
print("Decoded:", decoded)

Encoded: uvwxy zg
Decoded: abcde fg

Explanation:

• Encoding: The str.maketrans("abcdef", "uvwxyz") creates a mapping where: 'a' → 'u', 'b' → 'v', 'c' → 'w', etc. Applying translate() transforms the string into its encoded form.
• Decoding: A reverse mapping is created with str.maketrans("uvwxyz", "abcdef") to decode the string back to its original form.

Example 4: Combining Removal and Replacement

Let’s combine character removal and replacement for a more complex text-processing task.

Example:

import string  # Import the string module

s = "Python3.9 is awesome!"
# Create a translation table
table = str.maketrans({"P": "p", "y": "Y", "o": "0"})  # Only use a dictionary here
# Remove digits using translate's deletechars parameter
res = s.translate(table).translate(str.maketrans("", "", string.digits))
print(res)

pYthn. is awesme!

Explanation:

• Replacement: 'P' → 'p' (uppercase to lowercase transformation). 'y' → 'Y' (lowercase to uppercase transformation). 'o' → '0' (replace the letter 'o' with the number zero).
• Removal: string.digits ensures all numeric characters ("0123456789") are removed.