# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility
import re
regex = 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
"""
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 = re.finditer(regex, test_str, re.VERBOSE | re.MULTILINE | re.IGNORECASE)
for matchNum, match in enumerate(matches, start=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.
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