sort strings by numeric char number

sort string

#!/usr/bin/env python -*- coding: utf-8 -*-

import re
import unittest

def least_numeric(strings):
    return min(strings, key=lambda s: len(re.findall(r'\d', s)))

class TestLeastNumeric(unittest.TestCase):
    def test1(self):
        l1 = ['123', 'hello1234world', 'bang1']
        self.assertEqual(least_numeric(l1), 'bang1')
        
    def test2(self):
        l2 = ['1', 'bang!', 'helloworld33']
        self.assertEqual(least_numeric(l2), 'bang!')
        
    def test3(self):
        l3 = ['zang1', 'o 2', 'woo3']
        self.assertEqual(least_numeric(l3), 'zang1')

    def test4(self):
        l4 = ['fo-o', 'b', 'woolala']
        self.assertEqual(least_numeric(l4), 'fo-o')

if __name__ == '__main__':
    unittest.main()