Python - Remove all characters except letters and numbers

When it is required to remove all characters except for letters and numbers, regular expressions are used. A regular expression is defined, and the string is subjected to follow this expression.

Using Regular Expressions with re.sub()

The re.sub() function replaces all non-alphanumeric characters with an empty string ?

import re

my_string = "python123:, .@! abc"

print("The string is:")
print(my_string)

result = re.sub('[\W_]+', '', my_string)

print("The expected string is:")
print(result)

The output of the above code is ?

The string is:
python123:, .@! abc
The expected string is:
python123abc

Using isalnum() with List Comprehension

An alternative approach uses the isalnum() method to filter characters ?

my_string = "python123:, .@! abc"

print("The string is:")
print(my_string)

result = ''.join([char for char in my_string if char.isalnum()])

print("The filtered string is:")
print(result)

The string is:
python123:, .@! abc
The filtered string is:
python123abc

Using filter() with isalnum()

The filter() function provides a functional programming approach ?

my_string = "python123:, .@! abc"

print("The string is:")
print(my_string)

result = ''.join(filter(str.isalnum, my_string))

print("The filtered string is:")
print(result)

The string is:
python123:, .@! abc
The filtered string is:
python123abc

Comparison

Conclusion

Use re.sub() for complex pattern matching or large strings. For simple alphanumeric filtering, list comprehension with isalnum() is more readable and efficient.