import re
regex = re.compile(r"\[{2}([^|]*?)(?:\|(.*?))?\]{2}")
test_str = ("A [[2008 Iwate-Miyagi Nairiku earthquake|6.9 magnitude earthquake]] in Iwate Prefecture, Japan, kills 12 and injures more than 400\n\n"
"[[December 1]] A triangular [[Conjunction (astronomy)|conjunction]] formed by a new Moon, Venus and Jupiter is a [[Conjunction (astronomy)#2008|prominent sight]] in the evening sky. [[December 2]]\n")
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