regexp for a semver compliant pre-release

gistfile1.txt

# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility

import re

regex = r"([0-9]+)\.([0-9]+)\.([0-9]+)(?:-([0-9alpha|beta|rc.-]+))?(?:\+([0-9a-zA-Z.-]+))?"

test_str = ("0.0.1\n"
	"0.1.0-rc.3\n"
	"0.1.0-alpha.12\n"
	"1.1.1\n"
	"0.5.0-beta.3+dfashfjlkjhflksah\n"
	"0.5.0-alpha\n")

matches = re.finditer(regex, test_str, re.MULTILINE)

for matchNum, match in enumerate(matches):
    matchNum = matchNum + 1
    
    print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group()))
    
    for groupNum in range(0, len(match.groups())):
        groupNum = groupNum + 1
        
        print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum)))

# Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.