How to Extract Digits Only from a String in Python

This code uses a regular expression to remove all non-digit characters from a mixed string, returning only the digits.

Easy Python 3.9+ Aug 9, 2026 Strings & text 12 views 0 copies

regex string manipulation data cleaning

Python code

10 lines

Python 3.9+

import re

def extract_digits(text):
    """Return only the digits from the given text as a string."""
    return re.sub(r'\D', '', text)

if __name__ == "__main__":
    mixed = "abc123def456!@#789"
    result = extract_digits(mixed)
    print(result)

Output

stdout

123456789

How it works

The re.sub function scans the input string and replaces every match of the pattern \D (which matches any non-digit character) with an empty string. This effectively deletes all characters that are not digits. The result is a new string containing only the digit characters, preserving their original order. The function is pure and side-effect free, making it easy to reuse and test.

Common mistakes

Using `\d+` with `re.findall` and then joining, which is less direct and may miss individual digits if separated
Forgetting to handle non-string inputs, which would cause `TypeError`

Variations

Using a list comprehension with `str.isdigit()`: `''.join(c for c in text if c.isdigit())`
Using `re.findall(r'\d', text)` and joining the list

Real-world use cases

Cleaning phone numbers from user input that contains hyphens, spaces, or letters.
Extracting numeric IDs from log lines that mix text and digits.
Parsing order numbers or transaction references from imported data streams.

How to Extract Digits Only from a String in Python

Python code

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How it works

Common mistakes

Variations

Real-world use cases

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