Match Integers Of Any Length

Based on: StackOverflow

Preliminaries

# Load regex package
import re

Create some text

# Create a variable containing a text string
text = '21 scouts and 3 tanks fought against 4,003 protestors.'

Apply regex

# Find any character block that is a integer of any length
re.findall(r'[1-9](?:\d{0,2})(?:,\d{3})*(?:\.\d*[1-9])?|0?\.\d*[1-9]|0', text)
['21', '3', '4,003']

Explanation from Justin Morgan

[1-9](?:\d{0,2}) #A sequence of 1-3 numerals not starting with 0
(?:,\d{3})*      #Any number of three-digit groups, each preceded by a comma
(?:\.\d*[1-9])?  #Optionally, a decimal point followed by any number of digits not ending in 0
|                #OR...
0?\.\d*[1-9]     #Only the decimal portion, optionally preceded by a 0
|                #OR...
0                #Zero.