Python - Extract digits from given string

We need to extract the digit from the given string. For example we are given a string s=""abc123def456gh789" we need to extract all the numbers from the string so the output for the given string will become "123456789" In this article we will show different ways to extract digits from a string in Python methods like using regular expressions and basic string manipulation to get only the numbers from a string.

Using str.isdigit()

str.isdigit() method in Python is used to check if all characters in a string are digits. It returns True if all characters are digits (0-9) and there is at least one character otherwise, it returns False.

s = "abc123def456gh789"

# Extract digits using a loop and isdigit()
digits = ''.join(char for char in s if char.isdigit())

print(digits)

123456789

Explanation: We loop through each character in the string s and uses isdigit() to check if a character is a digit and only the digits are joined together into a new string which is printed as the result.

Using Regular Expressions (re.findall)

Using re.findall() in Python allows to extract all substrings that match a specific pattern such as digits, from a given string.

import re

s = "abc123def456gh789"

# Extract digits using regex
digits = ''.join(re.findall(r'\d', s))

print(digits)

123456789

Explanation:

• re.findall() function is used to find all digits (\d) in the string, returning them as a list of individual characters.
• ''.join() method combines the list of digits into a single string for the final result

Using str.translate() with str.maketrans()

str.translate() method combined with str.maketrans(), provides an efficient way to replace multiple characters or remove unwanted characters from a string in Python.

s = "abc123def456gh789"

# Extract digits using translate and maketrans
digits = s.translate(str.maketrans('', '', 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()'))

print(digits)

123456789

Explanation:

• str.maketrans('', '', 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()') creates a translation table that maps all lowercase and uppercase letters, as well as special characters, to None, effectively removing them from the string.
• s.translate() applies the translation table to the string s, removing all characters except the digits resulting in a string that contains only the numeric characters.