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652 lines
24 KiB
Python
652 lines
24 KiB
Python
# module 're' -- A collection of regular expression operations
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"""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's 8-bit clean: the strings being processed may
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contain both null bytes and characters whose high bit is set. Regular
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expression pattern strings may not contain null bytes, but can specify
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the null byte using the \\number notation. Characters with the high
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bit set may be included.
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Regular expressions can contain both special and ordinary
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characters. Most ordinary characters, like "A", "a", or "0", are the
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simplest 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.
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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 0 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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(?iLmsx) Set the I, L, M, S, or X flag for the RE.
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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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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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compile Compile a pattern into a RegexObject.
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escape Backslash all non-alphanumerics in a string.
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This module exports the following classes:
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RegexObject Holds a compiled regular expression pattern.
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MatchObject Contains information about pattern matches.
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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 as well as the string.
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"$" matches the end of lines as well as the string.
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S DOTALL "." matches any character at all, including the newline.
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X VERBOSE Ignore whitespaces and comments for nicer looking RE's.
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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 string
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from pcre import *
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#
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# First, the public part of the interface:
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#
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# pcre.error and re.error should be the same, since exceptions can be
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# raised from either module.
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# compilation flags
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I = IGNORECASE
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L = LOCALE
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M = MULTILINE
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S = DOTALL
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X = VERBOSE
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#
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#
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#
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_cache = {}
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_MAXCACHE = 20
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def _cachecompile(pattern, flags=0):
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key = (pattern, flags)
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try:
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return _cache[key]
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except KeyError:
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pass
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value = compile(pattern, flags)
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if len(_cache) >= _MAXCACHE:
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_cache.clear()
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_cache[key] = value
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return value
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def match(pattern, string, flags=0):
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"""match (pattern, string[, flags]) -> MatchObject or None
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If zero or more characters at the beginning of string match the
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regular expression pattern, return a corresponding MatchObject
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instance. Return None if the string does not match the pattern;
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note that this is different from a zero-length match.
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Note: If you want to locate a match anywhere in string, use
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search() instead.
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"""
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return _cachecompile(pattern, flags).match(string)
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def search(pattern, string, flags=0):
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"""search (pattern, string[, flags]) -> MatchObject or None
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Scan through string looking for a location where the regular
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expression pattern produces a match, and return a corresponding
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MatchObject instance. Return None if no position in the string
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matches the pattern; note that this is different from finding a
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zero-length match at some point in the string.
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"""
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return _cachecompile(pattern, flags).search(string)
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def sub(pattern, repl, string, count=0):
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"""sub(pattern, repl, string[, count=0]) -> string
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Return the string obtained by replacing the leftmost
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non-overlapping occurrences of pattern in string by the
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replacement repl. If the pattern isn't found, string is returned
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unchanged. repl can be a string or a function; if a function, it
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is called for every non-overlapping occurrence of pattern. The
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function takes a single match object argument, and returns the
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replacement string.
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The pattern may be a string or a regex object; if you need to
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specify regular expression flags, you must use a regex object, or
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use embedded modifiers in a pattern; e.g.
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sub("(?i)b+", "x", "bbbb BBBB") returns 'x x'.
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The optional argument count is the maximum number of pattern
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occurrences to be replaced; count must be a non-negative integer,
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and the default value of 0 means to replace all occurrences.
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"""
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if type(pattern) == type(''):
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pattern = _cachecompile(pattern)
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return pattern.sub(repl, string, count)
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def subn(pattern, repl, string, count=0):
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"""subn(pattern, repl, string[, count=0]) -> (string, num substitutions)
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Perform the same operation as sub(), but return a tuple
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(new_string, number_of_subs_made).
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"""
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if type(pattern) == type(''):
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pattern = _cachecompile(pattern)
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return pattern.subn(repl, string, count)
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def split(pattern, string, maxsplit=0):
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"""split(pattern, string[, maxsplit=0]) -> list of strings
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Split string by the occurrences of pattern. If capturing
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parentheses are used in pattern, then the text of all groups in
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the pattern are also returned as part of the resulting list. If
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maxsplit is nonzero, at most maxsplit splits occur, and the
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remainder of the string is returned as the final element of the
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list.
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"""
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if type(pattern) == type(''):
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pattern = _cachecompile(pattern)
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return pattern.split(string, maxsplit)
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def findall(pattern, string):
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"""findall(pattern, string) -> list
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Return a list of all non-overlapping matches of pattern in
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string. 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 has
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more than one group. Empty matches are included in the result.
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"""
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if type(pattern) == type(''):
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pattern = _cachecompile(pattern)
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return pattern.findall(string)
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def escape(pattern):
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"""escape(string) -> string
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Return string with all non-alphanumerics backslashed; this is
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useful if you want to match an arbitrary literal string that may
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have regular expression metacharacters in it.
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"""
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result = list(pattern)
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alphanum=string.letters+'_'+string.digits
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for i in range(len(pattern)):
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char = pattern[i]
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if char not in alphanum:
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if char=='\000': result[i] = '\\000'
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else: result[i] = '\\'+char
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return string.join(result, '')
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def compile(pattern, flags=0):
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"""compile(pattern[, flags]) -> RegexObject
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Compile a regular expression pattern into a regular expression
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object, which can be used for matching using its match() and
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search() methods.
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"""
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groupindex={}
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code=pcre_compile(pattern, flags, groupindex)
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return RegexObject(pattern, flags, code, groupindex)
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#
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# Class definitions
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#
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class RegexObject:
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"""Holds a compiled regular expression pattern.
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Methods:
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match Match the pattern to the beginning of a string.
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search Search a string for the presence of the pattern.
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sub Substitute occurrences of the 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 the pattern.
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findall Find all occurrences of the pattern in a string.
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"""
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def __init__(self, pattern, flags, code, groupindex):
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self.code = code
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self.flags = flags
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self.pattern = pattern
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self.groupindex = groupindex
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def search(self, string, pos=0, endpos=None):
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"""search(string[, pos][, endpos]) -> MatchObject or None
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Scan through string looking for a location where this regular
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expression produces a match, and return a corresponding
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MatchObject instance. Return None if no position in the string
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matches the pattern; note that this is different from finding
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a zero-length match at some point in the string. The optional
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pos and endpos parameters have the same meaning as for the
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match() method.
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"""
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if endpos is None or endpos>len(string):
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endpos=len(string)
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if endpos<pos: endpos=pos
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regs = self.code.match(string, pos, endpos, 0)
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if regs is None:
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return None
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self._num_regs=len(regs)
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return MatchObject(self,
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string,
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pos, endpos,
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regs)
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def match(self, string, pos=0, endpos=None):
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"""match(string[, pos][, endpos]) -> MatchObject or None
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If zero or more characters at the beginning of string match
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this regular expression, return a corresponding MatchObject
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instance. Return None if the string does not match the
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pattern; note that this is different from a zero-length match.
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Note: If you want to locate a match anywhere in string, use
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search() instead.
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The optional second parameter pos gives an index in the string
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where the search is to start; it defaults to 0. This is not
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completely equivalent to slicing the string; the '' pattern
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character matches at the real beginning of the string and at
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positions just after a newline, but not necessarily at the
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index where the search is to start.
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The optional parameter endpos limits how far the string will
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be searched; it will be as if the string is endpos characters
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long, so only the characters from pos to endpos will be
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searched for a match.
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"""
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if endpos is None or endpos>len(string):
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endpos=len(string)
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if endpos<pos: endpos=pos
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regs = self.code.match(string, pos, endpos, ANCHORED)
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if regs is None:
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return None
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self._num_regs=len(regs)
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return MatchObject(self,
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string,
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pos, endpos,
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regs)
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def sub(self, repl, string, count=0):
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"""sub(repl, string[, count=0]) -> string
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Return the string obtained by replacing the leftmost
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non-overlapping occurrences of the compiled pattern in string
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by the replacement repl. If the pattern isn't found, string is
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returned unchanged.
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Identical to the sub() function, using the compiled pattern.
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"""
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return self.subn(repl, string, count)[0]
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def subn(self, repl, source, count=0):
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"""subn(repl, string[, count=0]) -> tuple
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Perform the same operation as sub(), but return a tuple
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(new_string, number_of_subs_made).
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"""
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if count < 0:
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raise error, "negative substitution count"
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if count == 0:
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count = sys.maxint
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n = 0 # Number of matches
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pos = 0 # Where to start searching
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lastmatch = -1 # End of last match
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results = [] # Substrings making up the result
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end = len(source)
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if type(repl) is type(''):
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# See if repl contains group references
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try:
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repl = pcre_expand(_Dummy, repl)
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except:
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m = MatchObject(self, source, 0, end, [])
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repl = lambda m, repl=repl, expand=pcre_expand: expand(m, repl)
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else:
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m = None
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else:
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m = MatchObject(self, source, 0, end, [])
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match = self.code.match
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append = results.append
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while n < count and pos <= end:
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regs = match(source, pos, end, 0)
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if not regs:
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break
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self._num_regs = len(regs)
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i, j = regs[0]
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if i == j == lastmatch:
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# Empty match adjacent to previous match
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pos = pos + 1
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append(source[lastmatch:pos])
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continue
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if pos < i:
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append(source[pos:i])
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if m:
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m.pos = pos
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m.regs = regs
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append(repl(m))
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else:
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append(repl)
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pos = lastmatch = j
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if i == j:
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# Last match was empty; don't try here again
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pos = pos + 1
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append(source[lastmatch:pos])
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n = n + 1
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append(source[pos:])
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return (string.join(results, ''), n)
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def split(self, source, maxsplit=0):
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"""split(source[, maxsplit=0]) -> list of strings
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Split string by the occurrences of the compiled pattern. If
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capturing parentheses are used in the pattern, then the text
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of all groups in the pattern are also returned as part of the
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resulting list. If maxsplit is nonzero, at most maxsplit
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splits occur, and the remainder of the string is returned as
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the final element of the list.
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"""
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if maxsplit < 0:
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raise error, "negative split count"
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if maxsplit == 0:
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maxsplit = sys.maxint
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n = 0
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pos = 0
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lastmatch = 0
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results = []
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end = len(source)
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match = self.code.match
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append = results.append
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while n < maxsplit:
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regs = match(source, pos, end, 0)
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if not regs:
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break
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i, j = regs[0]
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if i == j:
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# Empty match
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if pos >= end:
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break
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pos = pos+1
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continue
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append(source[lastmatch:i])
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rest = regs[1:]
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if rest:
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for a, b in rest:
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if a == -1 or b == -1:
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group = None
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else:
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group = source[a:b]
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append(group)
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pos = lastmatch = j
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n = n + 1
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append(source[lastmatch:])
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return results
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def findall(self, source):
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"""findall(source) -> list
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Return a list of all non-overlapping matches of the compiled
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pattern in string. If one or more groups are present in the
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pattern, return a list of groups; this will be a list of
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tuples if the pattern has more than one group. Empty matches
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are included in the result.
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"""
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pos = 0
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end = len(source)
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results = []
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match = self.code.match
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append = results.append
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while pos <= end:
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regs = match(source, pos, end, 0)
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if not regs:
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break
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i, j = regs[0]
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rest = regs[1:]
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if not rest:
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gr = source[i:j]
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elif len(rest) == 1:
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a, b = rest[0]
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gr = source[a:b]
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else:
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gr = []
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for (a, b) in rest:
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gr.append(source[a:b])
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gr = tuple(gr)
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append(gr)
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pos = max(j, pos+1)
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return results
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# The following 3 functions were contributed by Mike Fletcher, and
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# allow pickling and unpickling of RegexObject instances.
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def __getinitargs__(self):
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return (None,None,None,None) # any 4 elements, to work around
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# problems with the
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# pickle/cPickle modules not yet
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# ignoring the __init__ function
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def __getstate__(self):
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return self.pattern, self.flags, self.groupindex
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def __setstate__(self, statetuple):
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self.pattern = statetuple[0]
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self.flags = statetuple[1]
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self.groupindex = statetuple[2]
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self.code = apply(pcre_compile, statetuple)
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class _Dummy:
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# Dummy class used by _subn_string(). Has 'group' to avoid core dump.
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group = None
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class MatchObject:
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"""Holds a compiled regular expression pattern.
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Methods:
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start Return the index of the start of a matched substring.
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end Return the index of the end of a matched substring.
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span Return a tuple of (start, end) of a matched substring.
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groups Return a tuple of all the subgroups of the match.
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group Return one or more subgroups of the match.
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groupdict Return a dictionary of all the named subgroups of the match.
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"""
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def __init__(self, re, string, pos, endpos, regs):
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self.re = re
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self.string = string
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self.pos = pos
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self.endpos = endpos
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self.regs = regs
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def start(self, g = 0):
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"""start([group=0]) -> int or None
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Return the index of the start of the substring matched by
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group; group defaults to zero (meaning the whole matched
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|
substring). Return None if group exists but did not contribute
|
|
to the match.
|
|
|
|
"""
|
|
if type(g) == type(''):
|
|
try:
|
|
g = self.re.groupindex[g]
|
|
except (KeyError, TypeError):
|
|
raise IndexError, 'group %s is undefined' % `g`
|
|
return self.regs[g][0]
|
|
|
|
def end(self, g = 0):
|
|
"""end([group=0]) -> int or None
|
|
|
|
Return the indices of the end of the substring matched by
|
|
group; group defaults to zero (meaning the whole matched
|
|
substring). Return None if group exists but did not contribute
|
|
to the match.
|
|
|
|
"""
|
|
if type(g) == type(''):
|
|
try:
|
|
g = self.re.groupindex[g]
|
|
except (KeyError, TypeError):
|
|
raise IndexError, 'group %s is undefined' % `g`
|
|
return self.regs[g][1]
|
|
|
|
def span(self, g = 0):
|
|
"""span([group=0]) -> tuple
|
|
|
|
Return the 2-tuple (m.start(group), m.end(group)). Note that
|
|
if group did not contribute to the match, this is (None,
|
|
None). Group defaults to zero (meaning the whole matched
|
|
substring).
|
|
|
|
"""
|
|
if type(g) == type(''):
|
|
try:
|
|
g = self.re.groupindex[g]
|
|
except (KeyError, TypeError):
|
|
raise IndexError, 'group %s is undefined' % `g`
|
|
return self.regs[g]
|
|
|
|
def groups(self, default=None):
|
|
"""groups([default=None]) -> tuple
|
|
|
|
Return a tuple containing all the subgroups of the match, from
|
|
1 up to however many groups are in the pattern. The default
|
|
argument is used for groups that did not participate in the
|
|
match.
|
|
|
|
"""
|
|
result = []
|
|
for g in range(1, self.re._num_regs):
|
|
a, b = self.regs[g]
|
|
if a == -1 or b == -1:
|
|
result.append(default)
|
|
else:
|
|
result.append(self.string[a:b])
|
|
return tuple(result)
|
|
|
|
def group(self, *groups):
|
|
"""group([group1, group2, ...]) -> string or tuple
|
|
|
|
Return one or more subgroups of the match. If there is a
|
|
single argument, the result is a single string; if there are
|
|
multiple arguments, the result is a tuple with one item per
|
|
argument. Without arguments, group1 defaults to zero (i.e. the
|
|
whole match is returned). If a groupN argument is zero, the
|
|
corresponding return value is the entire matching string; if
|
|
it is in the inclusive range [1..99], it is the string
|
|
matching the the corresponding parenthesized group. If a group
|
|
number is negative or larger than the number of groups defined
|
|
in the pattern, an IndexError exception is raised. If a group
|
|
is contained in a part of the pattern that did not match, the
|
|
corresponding result is None. If a group is contained in a
|
|
part of the pattern that matched multiple times, the last
|
|
match is returned.
|
|
|
|
If the regular expression uses the (?P<name>...) syntax, the
|
|
groupN arguments may also be strings identifying groups by
|
|
their group name. If a string argument is not used as a group
|
|
name in the pattern, an IndexError exception is raised.
|
|
|
|
"""
|
|
if len(groups) == 0:
|
|
groups = (0,)
|
|
result = []
|
|
for g in groups:
|
|
if type(g) == type(''):
|
|
try:
|
|
g = self.re.groupindex[g]
|
|
except (KeyError, TypeError):
|
|
raise IndexError, 'group %s is undefined' % `g`
|
|
if g >= len(self.regs):
|
|
raise IndexError, 'group %s is undefined' % `g`
|
|
a, b = self.regs[g]
|
|
if a == -1 or b == -1:
|
|
result.append(None)
|
|
else:
|
|
result.append(self.string[a:b])
|
|
if len(result) > 1:
|
|
return tuple(result)
|
|
elif len(result) == 1:
|
|
return result[0]
|
|
else:
|
|
return ()
|
|
|
|
def groupdict(self, default=None):
|
|
"""groupdict([default=None]) -> dictionary
|
|
|
|
Return a dictionary containing all the named subgroups of the
|
|
match, keyed by the subgroup name. The default argument is
|
|
used for groups that did not participate in the match.
|
|
|
|
"""
|
|
dict = {}
|
|
for name, index in self.re.groupindex.items():
|
|
a, b = self.regs[index]
|
|
if a == -1 or b == -1:
|
|
dict[name] = default
|
|
else:
|
|
dict[name] = self.string[a:b]
|
|
return dict
|