Python Program to Remove Punctuation from String

Use ''.join(char for char in text if char.isalnum() or char.isspace()) to remove punctuation from a string in Python.

Examples

InputHello, world!

OutputHello world

InputPython's syntax: simple, yet powerful.

OutputPythons syntax simple yet powerful

InputNo punctuation here

OutputNo punctuation here

How to Think About It

To remove punctuation, check each character in the string and keep it only if it is a letter, number, or space. Skip all punctuation marks by filtering them out.

Algorithm

1

Get the input string.

2

Create a new empty string to store result.

3

For each character in the input string, check if it is a letter, number, or space.

4

If yes, add it to the new string; if not, skip it.

5

Return or print the new string without punctuation.

Code

python

text = "Hello, world!"
clean_text = ''.join(char for char in text if char.isalnum() or char.isspace())
print(clean_text)

Output

Hello world

Dry Run

Let's trace the input 'Hello, world!' through the code.

1

Input string

text = 'Hello, world!'

2

Check each character

H (keep), e (keep), l (keep), l (keep), o (keep), , (skip), (keep), w (keep), o (keep), r (keep), l (keep), d (keep), ! (skip)

3

Build new string

clean_text = 'Hello world'

4

Print result

Output: Hello world

Character	Keep?
H	Yes
e	Yes
l	Yes
l	Yes
o	Yes
,	No
	Yes
w	Yes
o	Yes
r	Yes
l	Yes
d	Yes
!	No

Why This Works

Step 1: Filter characters

The code uses char.isalnum() to keep letters and numbers, and char.isspace() to keep spaces, removing punctuation.

Step 2: Join characters

It joins all kept characters into a new string without punctuation using ''.join().

Alternative Approaches

Using string.punctuation and str.translate

python

import string
text = "Hello, world!"
translator = str.maketrans('', '', string.punctuation)
clean_text = text.translate(translator)
print(clean_text)

This method is efficient and uses built-in translation table to remove all punctuation characters.

Using regular expressions

python

import re
text = "Hello, world!"
clean_text = re.sub(r'[^\w\s]', '', text)
print(clean_text)

This uses regex to remove all characters except word characters and whitespace.

Complexity: O(n) time, O(n) space

Time Complexity

The program checks each character once, so time grows linearly with string length.

Space Complexity

A new string is created to store the result, so space also grows linearly with input size.

Which Approach is Fastest?

Using str.translate with string.punctuation is generally faster than character-by-character filtering or regex.

Approach	Time	Space	Best For
Character filtering with isalnum/isspace	O(n)	O(n)	Simple and readable code
str.translate with string.punctuation	O(n)	O(n)	Fastest and efficient for large strings
Regular expressions	O(n)	O(n)	Flexible pattern matching, but slightly slower