325 lines
13 KiB
Python
325 lines
13 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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(?iLmsux) Set the I, L, M, S, U, or X flag for the RE (see 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].
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\D Matches any non-digit character; equivalent to the set [^0-9].
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\s Matches any whitespace character; equivalent to [ \t\n\r\f\v].
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\S Matches any non-whitespace character; equiv. to [^ \t\n\r\f\v].
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\w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_].
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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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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 RegexObject.
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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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Some of the functions in this module takes flags as optional parameters:
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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 Make \w, \W, \b, \B, dependent on the Unicode locale.
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This module also defines an exception 'error'.
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"""
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import sys
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import sre_compile
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import sre_parse
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# public symbols
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__all__ = [ "match", "search", "sub", "subn", "split", "findall",
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"compile", "purge", "template", "escape", "I", "L", "M", "S", "X",
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"U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
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"UNICODE", "error" ]
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__version__ = "2.2.1"
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# flags
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I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case
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L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
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U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale
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M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
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S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline
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X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments
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# sre extensions (experimental, don't rely on these)
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T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking
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DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation
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# sre exception
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error = sre_compile.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 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."""
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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 groups are present in the pattern, return a
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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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if sys.hexversion >= 0x02020000:
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__all__.append("finditer")
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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 cache"
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_cache.clear()
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_cache_repl.clear()
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def template(pattern, flags=0):
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"Compile a template pattern, returning a pattern object"
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return _compile(pattern, flags|T)
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_alphanum = frozenset(
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"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890")
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def escape(pattern):
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"Escape all non-alphanumeric characters in pattern."
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s = list(pattern)
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alphanum = _alphanum
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for i, c in enumerate(pattern):
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if c not in alphanum:
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if c == "\000":
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s[i] = "\\000"
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else:
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s[i] = "\\" + c
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return pattern[:0].join(s)
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# --------------------------------------------------------------------
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# internals
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_cache = {}
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_cache_repl = {}
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_pattern_type = type(sre_compile.compile("", 0))
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_MAXCACHE = 100
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def _compile(*key):
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# internal: compile pattern
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cachekey = (type(key[0]),) + key
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p = _cache.get(cachekey)
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if p is not None:
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return p
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pattern, flags = key
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if isinstance(pattern, _pattern_type):
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if flags:
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raise ValueError('Cannot process flags argument with a compiled pattern')
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return pattern
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if not sre_compile.isstring(pattern):
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raise TypeError, "first argument must be string or compiled pattern"
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try:
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p = sre_compile.compile(pattern, flags)
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except error, v:
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raise error, v # invalid expression
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if len(_cache) >= _MAXCACHE:
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_cache.clear()
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_cache[cachekey] = p
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return p
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def _compile_repl(*key):
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# internal: compile replacement pattern
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p = _cache_repl.get(key)
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if p is not None:
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return p
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repl, pattern = key
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try:
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p = sre_parse.parse_template(repl, pattern)
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except error, v:
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raise error, v # invalid expression
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if len(_cache_repl) >= _MAXCACHE:
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_cache_repl.clear()
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_cache_repl[key] = p
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return p
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def _expand(pattern, match, template):
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# internal: match.expand implementation hook
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template = sre_parse.parse_template(template, pattern)
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return sre_parse.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 sre_parse.expand_template(template, match)
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return filter
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# register myself for pickling
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import copy_reg
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def _pickle(p):
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return _compile, (p.pattern, p.flags)
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copy_reg.pickle(_pattern_type, _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 sre_constants import BRANCH, SUBPATTERN
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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 = sre_parse.Pattern()
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s.flags = flags
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for phrase, action in lexicon:
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p.append(sre_parse.SubPattern(s, [
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(SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))),
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]))
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s.groups = len(p)+1
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p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])
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self.scanner = sre_compile.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 1:
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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 hasattr(action, '__call__'):
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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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