mirror of https://github.com/python/cpython
400 lines
16 KiB
Python
400 lines
16 KiB
Python
#
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# Secret Labs' Regular Expression Engine
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#
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# re-compatible interface for the sre matching engine
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#
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# Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
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#
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# This version of the SRE library can be redistributed under CNRI's
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# Python 1.6 license. For any other use, please contact Secret Labs
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# AB (info@pythonware.com).
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#
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# Portions of this engine have been developed in cooperation with
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# CNRI. Hewlett-Packard provided funding for 1.6 integration and
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# other compatibility work.
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#
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r"""Support for regular expressions (RE).
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This module provides regular expression matching operations similar to
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those found in Perl. It supports both 8-bit and Unicode strings; both
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the pattern and the strings being processed can contain null bytes and
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characters outside the US ASCII range.
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Regular expressions can contain both special and ordinary characters.
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Most ordinary characters, like "A", "a", or "0", are the simplest
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regular expressions; they simply match themselves. You can
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concatenate ordinary characters, so last matches the string 'last'.
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The special characters are:
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"." Matches any character except a newline.
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"^" Matches the start of the string.
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"$" Matches the end of the string or just before the newline at
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the end of the string.
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"*" Matches 0 or more (greedy) repetitions of the preceding RE.
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Greedy means that it will match as many repetitions as possible.
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"+" Matches 1 or more (greedy) repetitions of the preceding RE.
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"?" Matches 0 or 1 (greedy) of the preceding RE.
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*?,+?,?? Non-greedy versions of the previous three special characters.
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{m,n} Matches from m to n repetitions of the preceding RE.
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{m,n}? Non-greedy version of the above.
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"\\" Either escapes special characters or signals a special sequence.
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[] Indicates a set of characters.
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A "^" as the first character indicates a complementing set.
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"|" A|B, creates an RE that will match either A or B.
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(...) Matches the RE inside the parentheses.
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The contents can be retrieved or matched later in the string.
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(?aiLmsux) The letters set the corresponding flags defined below.
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(?:...) Non-grouping version of regular parentheses.
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(?P<name>...) The substring matched by the group is accessible by name.
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(?P=name) Matches the text matched earlier by the group named name.
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(?#...) A comment; ignored.
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(?=...) Matches if ... matches next, but doesn't consume the string.
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(?!...) Matches if ... doesn't match next.
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(?<=...) Matches if preceded by ... (must be fixed length).
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(?<!...) Matches if not preceded by ... (must be fixed length).
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(?(id/name)yes|no) Matches yes pattern if the group with id/name matched,
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the (optional) no pattern otherwise.
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The special sequences consist of "\\" and a character from the list
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below. If the ordinary character is not on the list, then the
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resulting RE will match the second character.
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\number Matches the contents of the group of the same number.
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\A Matches only at the start of the string.
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\Z Matches only at the end of the string.
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\b Matches the empty string, but only at the start or end of a word.
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\B Matches the empty string, but not at the start or end of a word.
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\d Matches any decimal digit; equivalent to the set [0-9] in
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bytes patterns or string patterns with the ASCII flag.
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In string patterns without the ASCII flag, it will match the whole
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range of Unicode digits.
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\D Matches any non-digit character; equivalent to [^\d].
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\s Matches any whitespace character; equivalent to [ \t\n\r\f\v] in
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bytes patterns or string patterns with the ASCII flag.
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In string patterns without the ASCII flag, it will match the whole
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range of Unicode whitespace characters.
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\S Matches any non-whitespace character; equivalent to [^\s].
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\w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_]
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in bytes patterns or string patterns with the ASCII flag.
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In string patterns without the ASCII flag, it will match the
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range of Unicode alphanumeric characters (letters plus digits
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plus underscore).
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With LOCALE, it will match the set [0-9_] plus characters defined
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as letters for the current locale.
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\W Matches the complement of \w.
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\\ Matches a literal backslash.
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This module exports the following functions:
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match Match a regular expression pattern to the beginning of a string.
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fullmatch Match a regular expression pattern to all of a string.
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search Search a string for the presence of a pattern.
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sub Substitute occurrences of a pattern found in a string.
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subn Same as sub, but also return the number of substitutions made.
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split Split a string by the occurrences of a pattern.
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findall Find all occurrences of a pattern in a string.
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finditer Return an iterator yielding a Match object for each match.
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compile Compile a pattern into a Pattern object.
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purge Clear the regular expression cache.
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escape Backslash all non-alphanumerics in a string.
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Each function other than purge and escape can take an optional 'flags' argument
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consisting of one or more of the following module constants, joined by "|".
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A, L, and U are mutually exclusive.
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A ASCII For string patterns, make \w, \W, \b, \B, \d, \D
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match the corresponding ASCII character categories
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(rather than the whole Unicode categories, which is the
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default).
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For bytes patterns, this flag is the only available
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behaviour and needn't be specified.
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I IGNORECASE Perform case-insensitive matching.
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L LOCALE Make \w, \W, \b, \B, dependent on the current locale.
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M MULTILINE "^" matches the beginning of lines (after a newline)
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as well as the string.
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"$" matches the end of lines (before a newline) as well
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as the end of the string.
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S DOTALL "." matches any character at all, including the newline.
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X VERBOSE Ignore whitespace and comments for nicer looking RE's.
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U UNICODE For compatibility only. Ignored for string patterns (it
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is the default), and forbidden for bytes patterns.
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This module also defines an exception 'error'.
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"""
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import enum
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from . import _compiler, _parser
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import functools
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# public symbols
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__all__ = [
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"match", "fullmatch", "search", "sub", "subn", "split",
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"findall", "finditer", "compile", "purge", "template", "escape",
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"error", "Pattern", "Match", "A", "I", "L", "M", "S", "X", "U",
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"ASCII", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
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"UNICODE", "NOFLAG", "RegexFlag",
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]
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__version__ = "2.2.1"
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@enum.global_enum
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@enum._simple_enum(enum.IntFlag, boundary=enum.KEEP)
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class RegexFlag:
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NOFLAG = 0
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ASCII = A = _compiler.SRE_FLAG_ASCII # assume ascii "locale"
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IGNORECASE = I = _compiler.SRE_FLAG_IGNORECASE # ignore case
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LOCALE = L = _compiler.SRE_FLAG_LOCALE # assume current 8-bit locale
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UNICODE = U = _compiler.SRE_FLAG_UNICODE # assume unicode "locale"
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MULTILINE = M = _compiler.SRE_FLAG_MULTILINE # make anchors look for newline
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DOTALL = S = _compiler.SRE_FLAG_DOTALL # make dot match newline
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VERBOSE = X = _compiler.SRE_FLAG_VERBOSE # ignore whitespace and comments
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# sre extensions (experimental, don't rely on these)
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TEMPLATE = T = _compiler.SRE_FLAG_TEMPLATE # unknown purpose, deprecated
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DEBUG = _compiler.SRE_FLAG_DEBUG # dump pattern after compilation
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__str__ = object.__str__
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_numeric_repr_ = hex
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# sre exception
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error = _compiler.error
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# --------------------------------------------------------------------
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# public interface
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def match(pattern, string, flags=0):
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"""Try to apply the pattern at the start of the string, returning
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a Match object, or None if no match was found."""
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return _compile(pattern, flags).match(string)
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def fullmatch(pattern, string, flags=0):
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"""Try to apply the pattern to all of the string, returning
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a Match object, or None if no match was found."""
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return _compile(pattern, flags).fullmatch(string)
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def search(pattern, string, flags=0):
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"""Scan through string looking for a match to the pattern, returning
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a Match object, or None if no match was found."""
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return _compile(pattern, flags).search(string)
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def sub(pattern, repl, string, count=0, flags=0):
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"""Return the string obtained by replacing the leftmost
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non-overlapping occurrences of the pattern in string by the
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replacement repl. repl can be either a string or a callable;
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if a string, backslash escapes in it are processed. If it is
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a callable, it's passed the Match object and must return
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a replacement string to be used."""
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return _compile(pattern, flags).sub(repl, string, count)
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def subn(pattern, repl, string, count=0, flags=0):
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"""Return a 2-tuple containing (new_string, number).
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new_string is the string obtained by replacing the leftmost
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non-overlapping occurrences of the pattern in the source
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string by the replacement repl. number is the number of
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substitutions that were made. repl can be either a string or a
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callable; if a string, backslash escapes in it are processed.
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If it is a callable, it's passed the Match object and must
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return a replacement string to be used."""
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return _compile(pattern, flags).subn(repl, string, count)
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def split(pattern, string, maxsplit=0, flags=0):
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"""Split the source string by the occurrences of the pattern,
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returning a list containing the resulting substrings. If
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capturing parentheses are used in pattern, then the text of all
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groups in the pattern are also returned as part of the resulting
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list. If maxsplit is nonzero, at most maxsplit splits occur,
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and the remainder of the string is returned as the final element
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of the list."""
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return _compile(pattern, flags).split(string, maxsplit)
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def findall(pattern, string, flags=0):
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"""Return a list of all non-overlapping matches in the string.
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If one or more capturing groups are present in the pattern, return
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a list of groups; this will be a list of tuples if the pattern
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has more than one group.
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Empty matches are included in the result."""
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return _compile(pattern, flags).findall(string)
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def finditer(pattern, string, flags=0):
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"""Return an iterator over all non-overlapping matches in the
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string. For each match, the iterator returns a Match object.
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Empty matches are included in the result."""
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return _compile(pattern, flags).finditer(string)
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def compile(pattern, flags=0):
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"Compile a regular expression pattern, returning a Pattern object."
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return _compile(pattern, flags)
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def purge():
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"Clear the regular expression caches"
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_cache.clear()
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_cache2.clear()
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_compile_repl.cache_clear()
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def template(pattern, flags=0):
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"Compile a template pattern, returning a Pattern object, deprecated"
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import warnings
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warnings.warn("The re.template() function is deprecated "
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"as it is an undocumented function "
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"without an obvious purpose. "
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"Use re.compile() instead.",
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DeprecationWarning)
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with warnings.catch_warnings():
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warnings.simplefilter("ignore", DeprecationWarning) # warn just once
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return _compile(pattern, flags|T)
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# SPECIAL_CHARS
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# closing ')', '}' and ']'
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# '-' (a range in character set)
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# '&', '~', (extended character set operations)
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# '#' (comment) and WHITESPACE (ignored) in verbose mode
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_special_chars_map = {i: '\\' + chr(i) for i in b'()[]{}?*+-|^$\\.&~# \t\n\r\v\f'}
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def escape(pattern):
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"""
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Escape special characters in a string.
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"""
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if isinstance(pattern, str):
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return pattern.translate(_special_chars_map)
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else:
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pattern = str(pattern, 'latin1')
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return pattern.translate(_special_chars_map).encode('latin1')
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Pattern = type(_compiler.compile('', 0))
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Match = type(_compiler.compile('', 0).match(''))
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# --------------------------------------------------------------------
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# internals
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# Use the fact that dict keeps the insertion order.
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# _cache2 uses the simple FIFO policy which has better latency.
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# _cache uses the LRU policy which has better hit rate.
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_cache = {} # LRU
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_cache2 = {} # FIFO
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_MAXCACHE = 512
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_MAXCACHE2 = 256
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assert _MAXCACHE2 < _MAXCACHE
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def _compile(pattern, flags):
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# internal: compile pattern
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if isinstance(flags, RegexFlag):
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flags = flags.value
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try:
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return _cache2[type(pattern), pattern, flags]
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except KeyError:
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pass
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key = (type(pattern), pattern, flags)
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# Item in _cache should be moved to the end if found.
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p = _cache.pop(key, None)
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if p is None:
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if isinstance(pattern, Pattern):
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if flags:
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raise ValueError(
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"cannot process flags argument with a compiled pattern")
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return pattern
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if not _compiler.isstring(pattern):
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raise TypeError("first argument must be string or compiled pattern")
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if flags & T:
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import warnings
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warnings.warn("The re.TEMPLATE/re.T flag is deprecated "
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"as it is an undocumented flag "
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"without an obvious purpose. "
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"Don't use it.",
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DeprecationWarning)
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p = _compiler.compile(pattern, flags)
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if flags & DEBUG:
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return p
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if len(_cache) >= _MAXCACHE:
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# Drop the least recently used item.
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# next(iter(_cache)) is known to have linear amortized time,
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# but it is used here to avoid a dependency from using OrderedDict.
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# For the small _MAXCACHE value it doesn't make much of a difference.
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try:
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del _cache[next(iter(_cache))]
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except (StopIteration, RuntimeError, KeyError):
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pass
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# Append to the end.
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_cache[key] = p
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if len(_cache2) >= _MAXCACHE2:
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# Drop the oldest item.
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try:
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del _cache2[next(iter(_cache2))]
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except (StopIteration, RuntimeError, KeyError):
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pass
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_cache2[key] = p
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return p
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@functools.lru_cache(_MAXCACHE)
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def _compile_repl(repl, pattern):
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# internal: compile replacement pattern
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return _parser.parse_template(repl, pattern)
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def _expand(pattern, match, template):
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# internal: Match.expand implementation hook
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template = _parser.parse_template(template, pattern)
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return _parser.expand_template(template, match)
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def _subx(pattern, template):
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# internal: Pattern.sub/subn implementation helper
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template = _compile_repl(template, pattern)
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if not template[0] and len(template[1]) == 1:
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# literal replacement
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return template[1][0]
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def filter(match, template=template):
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return _parser.expand_template(template, match)
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return filter
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# register myself for pickling
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import copyreg
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def _pickle(p):
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return _compile, (p.pattern, p.flags)
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copyreg.pickle(Pattern, _pickle, _compile)
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# --------------------------------------------------------------------
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# experimental stuff (see python-dev discussions for details)
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class Scanner:
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def __init__(self, lexicon, flags=0):
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from ._constants import BRANCH, SUBPATTERN
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if isinstance(flags, RegexFlag):
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flags = flags.value
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self.lexicon = lexicon
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# combine phrases into a compound pattern
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p = []
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s = _parser.State()
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s.flags = flags
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for phrase, action in lexicon:
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gid = s.opengroup()
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p.append(_parser.SubPattern(s, [
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(SUBPATTERN, (gid, 0, 0, _parser.parse(phrase, flags))),
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]))
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s.closegroup(gid, p[-1])
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p = _parser.SubPattern(s, [(BRANCH, (None, p))])
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self.scanner = _compiler.compile(p)
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def scan(self, string):
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result = []
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append = result.append
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match = self.scanner.scanner(string).match
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i = 0
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while True:
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m = match()
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if not m:
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break
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j = m.end()
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if i == j:
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break
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action = self.lexicon[m.lastindex-1][1]
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if callable(action):
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self.match = m
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action = action(self, m.group())
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if action is not None:
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append(action)
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i = j
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return result, string[i:]
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