Extract Numbers From a String in Python

This tutorial explains how to get numbers from a string in Python. It also lists some example codes to further clarify the concept using different approaches.

Use List Comprehension to Extract Numbers From a String

Numbers from a string can be obtained by simple list comprehension. split() method is used to convert string to a list of characters and isdigit() method is used to check if a digit is found through the iteration.

A basis code example is given as:

temp_string = "Hi my age is 32 years and 250 days12"
print(temp_string)

numbers = [int(temp)for temp in temp_string.split() if temp.isdigit()]

print(numbers)

Output:

Hi my age is 32 years and 250 days12
[32, 250]

However, this code does not identify numbers that come with alphabets.

Use the re Module to Extract Numbers From a String

The re module of Python also provides functions that can search through the string and extract results. The re module provides with the findall() method that returns a list of all the matches. An example code is given below:

import re

temp_string = "Hi my age is 32 years and 250.5 days12"
print(temp_string)
print([float(s) for s in re.findall(r'-?\d+\.?\d*', temp_string)])

Output:

Hi my age is 32 years and 250.5 days12
[32.0, 250.5, 12.0]

The RegEx solution works for negative and positive numbers and overcomes the problem encountered in the List Comprehension approach.