import re
regex = re.compile(r"""
^ # begin of string
(?:(?!(?:\1|\2|\3)).)*? # ungreedy anything that is not captured by group 1,2,or 3
( # 1th capturing group
(?:\brain\b|\bsunlight\b|\bbark) # Alternation group (answers) \b word-boundaries as needed
)
(?:(?!(?:\1|\2|\3)).)*? # ungreedy anything that is not captured by group 1,2,or 3
( # 3th capturing group
(?:(?!(?:\1|\3))(?:\brain\b|\bsunlight\b|\bbark)) # Answers not captured in group 1 or 3
)
(?:(?!(?:\1|\2|\3)).)*? # ungreedy anything that is not captured by group 1,2,or 3
( # 4th capturing group
(?:(?!(?:\2|\3))(?:\brain\b|\bsunlight\b|\bbark)) # Answers not captured by group 2 or 3
)
(?:(?!(?:\1|\2|\3)).)* # anything that is not captured by group 1,2,or 3
$ # end of string
""", flags=re.VERBOSE | re.MULTILINE | re.IGNORECASE)
test_str = ("rain. bright sunlight. a dog's bark.\n"
"rain. bright rain. a dog's bark.\n"
"Barksunlight rain\n"
"bark sun rain\n"
"bar sunlight sunlight\n"
"Rain rain rain\n"
"sunlight rain bark\n"
"Barking dog, sunlight, rainforest\n"
"Barking elephant, green Sunlight, purple rain and other non-sense\n\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