Lichen

lib/re.py

203:e28858d7f9d5
2016-11-21 Paul Boddie Added alias serialisation in order to preserve origin information for imported instances in the cached data.
     1 #     2 # Secret Labs' Regular Expression Engine     3 #     4 # re-compatible interface for the sre matching engine     5 #     6 # Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.     7 #     8 # This version of the SRE library can be redistributed under CNRI's     9 # Python 1.6 license.  For any other use, please contact Secret Labs    10 # AB (info@pythonware.com).    11 #    12 # Portions of this engine have been developed in cooperation with    13 # CNRI.  Hewlett-Packard provided funding for 1.6 integration and    14 # other compatibility work.    15 #    16     17 r"""Support for regular expressions (RE).    18     19 This module provides regular expression matching operations similar to    20 those found in Perl.  It supports both 8-bit and Unicode strings; both    21 the pattern and the strings being processed can contain null bytes and    22 characters outside the US ASCII range.    23     24 Regular expressions can contain both special and ordinary characters.    25 Most ordinary characters, like "A", "a", or "0", are the simplest    26 regular expressions; they simply match themselves.  You can    27 concatenate ordinary characters, so last matches the string 'last'.    28     29 The special characters are:    30     "."      Matches any character except a newline.    31     "^"      Matches the start of the string.    32     "$"      Matches the end of the string or just before the newline at    33              the end of the string.    34     "*"      Matches 0 or more (greedy) repetitions of the preceding RE.    35              Greedy means that it will match as many repetitions as possible.    36     "+"      Matches 1 or more (greedy) repetitions of the preceding RE.    37     "?"      Matches 0 or 1 (greedy) of the preceding RE.    38     *?,+?,?? Non-greedy versions of the previous three special characters.    39     {m,n}    Matches from m to n repetitions of the preceding RE.    40     {m,n}?   Non-greedy version of the above.    41     "\\"     Either escapes special characters or signals a special sequence.    42     []       Indicates a set of characters.    43              A "^" as the first character indicates a complementing set.    44     "|"      A|B, creates an RE that will match either A or B.    45     (...)    Matches the RE inside the parentheses.    46              The contents can be retrieved or matched later in the string.    47     (?iLmsux) Set the I, L, M, S, U, or X flag for the RE (see below).    48     (?:...)  Non-grouping version of regular parentheses.    49     (?P<name>...) The substring matched by the group is accessible by name.    50     (?P=name)     Matches the text matched earlier by the group named name.    51     (?#...)  A comment; ignored.    52     (?=...)  Matches if ... matches next, but doesn't consume the string.    53     (?!...)  Matches if ... doesn't match next.    54     (?<=...) Matches if preceded by ... (must be fixed length).    55     (?<!...) Matches if not preceded by ... (must be fixed length).    56     (?(id/name)yes|no) Matches yes pattern if the group with id/name matched,    57                        the (optional) no pattern otherwise.    58     59 The special sequences consist of "\\" and a character from the list    60 below.  If the ordinary character is not on the list, then the    61 resulting RE will match the second character.    62     \number  Matches the contents of the group of the same number.    63     \A       Matches only at the start of the string.    64     \Z       Matches only at the end of the string.    65     \b       Matches the empty string, but only at the start or end of a word.    66     \B       Matches the empty string, but not at the start or end of a word.    67     \d       Matches any decimal digit; equivalent to the set [0-9].    68     \D       Matches any non-digit character; equivalent to the set [^0-9].    69     \s       Matches any whitespace character; equivalent to [ \t\n\r\f\v].    70     \S       Matches any non-whitespace character; equiv. to [^ \t\n\r\f\v].    71     \w       Matches any alphanumeric character; equivalent to [a-zA-Z0-9_].    72              With LOCALE, it will match the set [0-9_] plus characters defined    73              as letters for the current locale.    74     \W       Matches the complement of \w.    75     \\       Matches a literal backslash.    76     77 This module exports the following functions:    78     match    Match a regular expression pattern to the beginning of a string.    79     search   Search a string for the presence of a pattern.    80     sub      Substitute occurrences of a pattern found in a string.    81     subn     Same as sub, but also return the number of substitutions made.    82     split    Split a string by the occurrences of a pattern.    83     findall  Find all occurrences of a pattern in a string.    84     finditer Return an iterator yielding a match object for each match.    85     compile  Compile a pattern into a RegexObject.    86     purge    Clear the regular expression cache.    87     escape   Backslash all non-alphanumerics in a string.    88     89 Some of the functions in this module takes flags as optional parameters:    90     I  IGNORECASE  Perform case-insensitive matching.    91     L  LOCALE      Make \w, \W, \b, \B, dependent on the current locale.    92     M  MULTILINE   "^" matches the beginning of lines (after a newline)    93                    as well as the string.    94                    "$" matches the end of lines (before a newline) as well    95                    as the end of the string.    96     S  DOTALL      "." matches any character at all, including the newline.    97     X  VERBOSE     Ignore whitespace and comments for nicer looking RE's.    98     U  UNICODE     Make \w, \W, \b, \B, dependent on the Unicode locale.    99    100 This module also defines an exception 'error'.   101    102 """   103    104 from sre_constants import BRANCH, SUBPATTERN   105 import sys   106 import sre_compile   107 import sre_parse   108    109 # public symbols   110 __all__ = [ "match", "search", "sub", "subn", "split", "findall",   111     "compile", "purge", "template", "escape", "I", "L", "M", "S", "X",   112     "U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",   113     "UNICODE", "error" ]   114    115 __version__ = "2.2.1"   116    117 # flags   118 I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case   119 L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale   120 U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale   121 M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline   122 S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline   123 X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments   124    125 # sre extensions (experimental, don't rely on these)   126 T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking   127 DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation   128    129 # sre exception   130 error = sre_compile.error   131    132 # --------------------------------------------------------------------   133 # public interface   134    135 def match(pattern, string, flags=0):   136     """Try to apply the pattern at the start of the string, returning   137     a match object, or None if no match was found."""   138     return _compile(pattern, flags).match(string)   139    140 def search(pattern, string, flags=0):   141     """Scan through string looking for a match to the pattern, returning   142     a match object, or None if no match was found."""   143     return _compile(pattern, flags).search(string)   144    145 def sub(pattern, repl, string, count=0, flags=0):   146     """Return the string obtained by replacing the leftmost   147     non-overlapping occurrences of the pattern in string by the   148     replacement repl.  repl can be either a string or a callable;   149     if a string, backslash escapes in it are processed.  If it is   150     a callable, it's passed the match object and must return   151     a replacement string to be used."""   152     return _compile(pattern, flags).sub(repl, string, count)   153    154 def subn(pattern, repl, string, count=0, flags=0):   155     """Return a 2-tuple containing (new_string, number).   156     new_string is the string obtained by replacing the leftmost   157     non-overlapping occurrences of the pattern in the source   158     string by the replacement repl.  number is the number of   159     substitutions that were made. repl can be either a string or a   160     callable; if a string, backslash escapes in it are processed.   161     If it is a callable, it's passed the match object and must   162     return a replacement string to be used."""   163     return _compile(pattern, flags).subn(repl, string, count)   164    165 def split(pattern, string, maxsplit=0, flags=0):   166     """Split the source string by the occurrences of the pattern,   167     returning a list containing the resulting substrings."""   168     return _compile(pattern, flags).split(string, maxsplit)   169    170 def findall(pattern, string, flags=0):   171     """Return a list of all non-overlapping matches in the string.   172    173     If one or more groups are present in the pattern, return a   174     list of groups; this will be a list of tuples if the pattern   175     has more than one group.   176    177     Empty matches are included in the result."""   178     return _compile(pattern, flags).findall(string)   179    180 if sys.hexversion >= 0x02020000:   181     __all__.append("finditer")   182     def finditer(pattern, string, flags=0):   183         """Return an iterator over all non-overlapping matches in the   184         string.  For each match, the iterator returns a match object.   185    186         Empty matches are included in the result."""   187         return _compile(pattern, flags).finditer(string)   188    189 def compile(pattern, flags=0):   190     "Compile a regular expression pattern, returning a pattern object."   191     return _compile(pattern, flags)   192    193 def purge():   194     "Clear the regular expression cache"   195     _cache.clear()   196     _cache_repl.clear()   197    198 def template(pattern, flags=0):   199     "Compile a template pattern, returning a pattern object"   200     return _compile(pattern, flags|T)   201    202 _alphanum = frozenset(   203     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")   204    205 def escape(pattern):   206     "Escape all non-alphanumeric characters in pattern."   207     s = list(pattern)   208     alphanum = _alphanum   209     for i, c in enumerate(pattern):   210         if c not in alphanum:   211             if c == "\000":   212                 s[i] = "\\000"   213             else:   214                 s[i] = "\\" + c   215     return pattern[:0].join(s)   216    217 # --------------------------------------------------------------------   218 # internals   219    220 _cache = {}   221 _cache_repl = {}   222    223 _pattern_type = type(sre_compile.compile("", 0))   224    225 _MAXCACHE = 100   226    227 def _compile(*key):   228     # internal: compile pattern   229     cachekey = (type(key[0]),) + key   230     p = _cache.get(cachekey)   231     if p is not None:   232         return p   233     pattern, flags = key   234     if isinstance(pattern, _pattern_type):   235         if flags:   236             raise ValueError('Cannot process flags argument with a compiled pattern')   237         return pattern   238     if not sre_compile.isstring(pattern):   239         raise TypeError, "first argument must be string or compiled pattern"   240     try:   241         p = sre_compile.compile(pattern, flags)   242     except error, v:   243         raise error, v # invalid expression   244     if len(_cache) >= _MAXCACHE:   245         _cache.clear()   246     _cache[cachekey] = p   247     return p   248    249 def _compile_repl(*key):   250     # internal: compile replacement pattern   251     p = _cache_repl.get(key)   252     if p is not None:   253         return p   254     repl, pattern = key   255     try:   256         p = sre_parse.parse_template(repl, pattern)   257     except error, v:   258         raise error, v # invalid expression   259     if len(_cache_repl) >= _MAXCACHE:   260         _cache_repl.clear()   261     _cache_repl[key] = p   262     return p   263    264 def _expand(pattern, match, template):   265     # internal: match.expand implementation hook   266     template = sre_parse.parse_template(template, pattern)   267     return sre_parse.expand_template(template, match)   268    269 def _subx(pattern, template):   270     # internal: pattern.sub/subn implementation helper   271     template = _compile_repl(template, pattern)   272     if not template[0] and len(template[1]) == 1:   273         # literal replacement   274         return template[1][0]   275     def filter(match, template=template):   276         return sre_parse.expand_template(template, match)   277     return filter   278    279 # --------------------------------------------------------------------   280 # experimental stuff (see python-dev discussions for details)   281    282 class Scanner:   283     def __init__(self, lexicon, flags=0):   284         self.lexicon = lexicon   285         # combine phrases into a compound pattern   286         p = []   287         s = sre_parse.Pattern()   288         s.flags = flags   289         for phrase, action in lexicon:   290             p.append(sre_parse.SubPattern(s, [   291                 (SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))),   292                 ]))   293         s.groups = len(p)+1   294         p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])   295         self.scanner = sre_compile.compile(p)   296     def scan(self, string):   297         result = []   298         append = result.append   299         match = self.scanner.scanner(string).match   300         i = 0   301         while 1:   302             m = match()   303             if not m:   304                 break   305             j = m.end()   306             if i == j:   307                 break   308             action = self.lexicon[m.lastindex-1][1]   309             if hasattr(action, '__call__'):   310                 self.match = m   311                 action = action(self, m.group())   312             if action is not None:   313                 append(action)   314             i = j   315         return result, string[i:]