Python Regular Expression: Validate American Style Comma Separated Integers

match_comma_numbers.py

# Regular expression to validate if a string is a valid integer with
# commas separating thousands, millions, billions and so on
import re

# start with some test cases:
good_tests = ['1', '12', '123', '1,234', '12,345', '123,456',
              '1,234,567', '12,345,678', '123,456,789']
fail_tests = ['1234', '1,2345', '12,34', '1,2', '1,23', '1.2', '1,234.5']

# implement a test harness
class TestPattern:
    def __init__(self, good, bad): 
        self.good = good 
        self.bad = bad 
    def __call__(self, pattern): 
        return all((pattern.match(g) for g in self.good)) and not any((pattern.match(b) for b in self.bad))

# instantiate a tester with our test cases:
test = TestPattern(good_tests, fail_tests)

# here's a pattern:
pattern = re.compile(r'^\d{1,3}(,\d{3})*$')

# use our tester:
test(pattern)
# return True