import re
regex = re.compile(r"^-?(?:(?:0|[1-9][0-9]*)(?:,[0-9]+)?|[1-9][0-9]{1,2}(?:,[0-9]{3})+)$", flags=re.MULTILINE)
test_str = ("123,456,789\n"
"-12,34\n"
"1234\n"
"-8\n"
"0,12\n"
"1,2,345\n"
"0")
matches = regex.finditer(test_str)
for match_num, match in enumerate(matches, start=1):
print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}")
for group_num, group in enumerate(match.groups(), start=1):
print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Python, please visit: https://docs.python.org/3/library/re.html