# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility
import re
regex = r"""
# match a body pattern alone on a line
^\g<body>$
# we'll use (?<name>...){0} to define the pattern \g<name>
# without having to match the pattern at the current position
# a body pattern matches
(?<body>
# a sequence of
(?: [^\[\]{}()\n] # non-delimiters
| \g<parens> # parenthesized pattern
| \g<square_brackets> # bracketed pattern
| \g<curly_braces> # braced pattern
)*
){0}
# a parenthesized pattern matches
(?<parens>
\( # an open paren
\g<body> # a valid body
\) # a close paren
){0}
# a bracketed pattern matches
(?<square_brackets>
\[ # an open square bracket
\g<body> # a valid body
\] # a close square bracket
){0}
# a braced pattern matches
(?<curly_braces>
\{ # an open curly brace
\g<body> # a valid body
\} # a close curly brace
){0}
"""
test_str = ("matches:\n"
"a plain string\n"
"a string containing (matched parens) [matched brackets] and {matched braces}\n"
"nested (parens (within) parens)\n"
"nested [parens (within) brackets]\n"
"()()[({({[]})[({})]})]\n\n"
"non-matches:\n"
"(unbalanced parens\n"
"([balanced but misordered)]")
matches = re.finditer(regex, test_str, re.MULTILINE | re.VERBOSE)
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