Remove non-alphanumeric characters from a Python string

This post will discuss how to remove non-alphanumeric characters from a string in Python.

1. Using regular expressions

A simple solution is to use regular expressions for removing non-alphanumeric characters from a string. The idea is to use the special character \W, which matches any character which is not a word character.

import re

if __name__ == '__main__':

input = "Welcome, User_12!!"

s = re.sub(r'\W+', '', input)

print(s) # WelcomeUser_12

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The \W is equivalent of [^a-zA-Z0-9_], which excludes all numbers and letters along with underscores. If you need to remove underscores as well, you can do like:

import re

if __name__ == '__main__':

input = "Welcome, User_12!!"

s = re.sub(r'[^a-zA-Z0-9]', '', input)

print(s) # WelcomeUser12

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If the expression is used several times in a single program, you should compile and save the resulting regular expression object for reuse.

import re

if __name__ == '__main__':

input = "Welcome, User_12!!"

pattern = re.compile('\W')

s = re.sub(pattern, '', input)

print(s) # WelcomeUser_12

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2. Using `isalnum()` function

Another option is to filter the string that matches with the isalnum() function. It returns true if all characters in the string are alphanumeric, false otherwise.

if __name__ == '__main__':

input = "Welcome, User_12!!"

s = ''.join(filter(str.isalnum, input))

print(s) # WelcomeUser12

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This is equivalent to:

if __name__ == '__main__':

input = "Welcome, User_12!!"

s = ''.join(c for c in input if c.isalnum())

print(s) # WelcomeUser12

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That’s all about removing non-alphanumeric characters from a string in Python.

Also See:

Remove specific characters from a Python string

Remove Punctuations from a Python string

Remove non-alphanumeric characters from a Python string

1. Using regular expressions

2. Using isalnum() function

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2. Using `isalnum()` function