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 (?aiLmsux) Set the A, 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 umber Matches the contents of the group of the same number. 63 A Matches only at the start of the string. 64 Matches only at the end of the string. 65 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] in 68 bytes patterns or string patterns with the ASCII flag. 69 In string patterns without the ASCII flag, it will match the whole 70 range of Unicode digits. 71 D Matches any non-digit character; equivalent to [^d]. 72 s Matches any whitespace character; equivalent to [ fv] in 73 bytes patterns or string patterns with the ASCII flag. 74 In string patterns without the ASCII flag, it will match the whole 75 range of Unicode whitespace characters. 76 S Matches any non-whitespace character; equivalent to [^s]. 77 w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_] 78 in bytes patterns or string patterns with the ASCII flag. 79 In string patterns without the ASCII flag, it will match the 80 range of Unicode alphanumeric characters (letters plus digits 81 plus underscore). 82 With LOCALE, it will match the set [0-9_] plus characters defined 83 as letters for the current locale. 84 W Matches the complement of w. 85 \ Matches a literal backslash. 86 87 This module exports the following functions: 88 match Match a regular expression pattern to the beginning of a string. 89 fullmatch Match a regular expression pattern to all of a string. 90 search Search a string for the presence of a pattern. 91 sub Substitute occurrences of a pattern found in a string. 92 subn Same as sub, but also return the number of substitutions made. 93 split Split a string by the occurrences of a pattern. 94 findall Find all occurrences of a pattern in a string. 95 finditer Return an iterator yielding a match object for each match. 96 compile Compile a pattern into a RegexObject. 97 purge Clear the regular expression cache. 98 escape Backslash all non-alphanumerics in a string. 99 100 Some of the functions in this module takes flags as optional parameters: 101 A ASCII For string patterns, make w, W, , B, d, D 102 match the corresponding ASCII character categories 103 (rather than the whole Unicode categories, which is the 104 default). 105 For bytes patterns, this flag is the only available 106 behaviour and needn't be specified. 107 I IGNORECASE Perform case-insensitive matching. 108 L LOCALE Make w, W, , B, dependent on the current locale. 109 M MULTILINE "^" matches the beginning of lines (after a newline) 110 as well as the string. 111 "$" matches the end of lines (before a newline) as well 112 as the end of the string. 113 S DOTALL "." matches any character at all, including the newline. 114 X VERBOSE Ignore whitespace and comments for nicer looking RE's. 115 U UNICODE For compatibility only. Ignored for string patterns (it 116 is the default), and forbidden for bytes patterns. 117 118 This module also defines an exception 'error'. 119 120 """ 121 122 import enum 123 import sre_compile 124 import sre_parse 125 import functools 126 try: 127 import _locale 128 except ImportError: 129 _locale = None 130 131 # public symbols 132 __all__ = [ 133 "match", "fullmatch", "search", "sub", "subn", "split", 134 "findall", "finditer", "compile", "purge", "template", "escape", 135 "error", "A", "I", "L", "M", "S", "X", "U", 136 "ASCII", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE", 137 "UNICODE", 138 ] 139 140 __version__ = "2.2.1" 141 142 class RegexFlag(enum.IntFlag): 143 ASCII = sre_compile.SRE_FLAG_ASCII # assume ascii "locale" 144 IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case 145 LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale 146 UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode "locale" 147 MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline 148 DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline 149 VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments 150 A = ASCII 151 I = IGNORECASE 152 L = LOCALE 153 U = UNICODE 154 M = MULTILINE 155 S = DOTALL 156 X = VERBOSE 157 # sre extensions (experimental, don't rely on these) 158 TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking 159 T = TEMPLATE 160 DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation 161 globals().update(RegexFlag.__members__) 162 163 # sre exception 164 error = sre_compile.error 165 166 # -------------------------------------------------------------------- 167 # public interface 168 169 def match(pattern, string, flags=0): 170 """Try to apply the pattern at the start of the string, returning 171 a match object, or None if no match was found.""" 172 return _compile(pattern, flags).match(string) 173 174 def fullmatch(pattern, string, flags=0): 175 """Try to apply the pattern to all of the string, returning 176 a match object, or None if no match was found.""" 177 return _compile(pattern, flags).fullmatch(string) 178 179 def search(pattern, string, flags=0): 180 """Scan through string looking for a match to the pattern, returning 181 a match object, or None if no match was found.""" 182 return _compile(pattern, flags).search(string) 183 184 def sub(pattern, repl, string, count=0, flags=0): 185 """Return the string obtained by replacing the leftmost 186 non-overlapping occurrences of the pattern in string by the 187 replacement repl. repl can be either a string or a callable; 188 if a string, backslash escapes in it are processed. If it is 189 a callable, it's passed the match object and must return 190 a replacement string to be used.""" 191 return _compile(pattern, flags).sub(repl, string, count) 192 193 def subn(pattern, repl, string, count=0, flags=0): 194 """Return a 2-tuple containing (new_string, number). 195 new_string is the string obtained by replacing the leftmost 196 non-overlapping occurrences of the pattern in the source 197 string by the replacement repl. number is the number of 198 substitutions that were made. repl can be either a string or a 199 callable; if a string, backslash escapes in it are processed. 200 If it is a callable, it's passed the match object and must 201 return a replacement string to be used.""" 202 return _compile(pattern, flags).subn(repl, string, count) 203 204 def split(pattern, string, maxsplit=0, flags=0): 205 """Split the source string by the occurrences of the pattern, 206 returning a list containing the resulting substrings. If 207 capturing parentheses are used in pattern, then the text of all 208 groups in the pattern are also returned as part of the resulting 209 list. If maxsplit is nonzero, at most maxsplit splits occur, 210 and the remainder of the string is returned as the final element 211 of the list.""" 212 return _compile(pattern, flags).split(string, maxsplit) 213 214 def findall(pattern, string, flags=0): 215 """Return a list of all non-overlapping matches in the string. 216 217 If one or more capturing groups are present in the pattern, return 218 a list of groups; this will be a list of tuples if the pattern 219 has more than one group. 220 221 Empty matches are included in the result.""" 222 return _compile(pattern, flags).findall(string) 223 224 def finditer(pattern, string, flags=0): 225 """Return an iterator over all non-overlapping matches in the 226 string. For each match, the iterator returns a match object. 227 228 Empty matches are included in the result.""" 229 return _compile(pattern, flags).finditer(string) 230 231 def compile(pattern, flags=0): 232 "Compile a regular expression pattern, returning a pattern object." 233 return _compile(pattern, flags) 234 235 def purge(): 236 "Clear the regular expression caches" 237 _cache.clear() 238 _compile_repl.cache_clear() 239 240 def template(pattern, flags=0): 241 "Compile a template pattern, returning a pattern object" 242 return _compile(pattern, flags|T) 243 244 _alphanum_str = frozenset( 245 "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890") 246 _alphanum_bytes = frozenset( 247 b"_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890") 248 249 def escape(pattern): 250 """ 251 Escape all the characters in pattern except ASCII letters, numbers and '_'. 252 """ 253 if isinstance(pattern, str): 254 alphanum = _alphanum_str 255 s = list(pattern) 256 for i, c in enumerate(pattern): 257 if c not in alphanum: 258 if c == " 00": 259 s[i] = "\000" 260 else: 261 s[i] = "\" + c 262 return "".join(s) 263 else: 264 alphanum = _alphanum_bytes 265 s = [] 266 esc = ord(b"\") 267 for c in pattern: 268 if c in alphanum: 269 s.append(c) 270 else: 271 if c == 0: 272 s.extend(b"\000") 273 else: 274 s.append(esc) 275 s.append(c) 276 return bytes(s) 277 278 # -------------------------------------------------------------------- 279 # internals 280 281 _cache = {} 282 283 _pattern_type = type(sre_compile.compile("", 0)) 284 285 _MAXCACHE = 512 286 def _compile(pattern, flags): 287 # internal: compile pattern 288 try: 289 p, loc = _cache[type(pattern), pattern, flags] 290 if loc is None or loc == _locale.setlocale(_locale.LC_CTYPE): 291 return p 292 except KeyError: 293 pass 294 if isinstance(pattern, _pattern_type): 295 if flags: 296 raise ValueError( 297 "cannot process flags argument with a compiled pattern") 298 return pattern 299 if not sre_compile.isstring(pattern): 300 raise TypeError("first argument must be string or compiled pattern") 301 p = sre_compile.compile(pattern, flags) 302 if not (flags & DEBUG): 303 if len(_cache) >= _MAXCACHE: 304 _cache.clear() 305 if p.flags & LOCALE: 306 if not _locale: 307 return p 308 loc = _locale.setlocale(_locale.LC_CTYPE) 309 else: 310 loc = None 311 _cache[type(pattern), pattern, flags] = p, loc 312 return p 313 314 @functools.lru_cache(_MAXCACHE) 315 def _compile_repl(repl, pattern): 316 # internal: compile replacement pattern 317 return sre_parse.parse_template(repl, pattern) 318 319 def _expand(pattern, match, template): 320 # internal: match.expand implementation hook 321 template = sre_parse.parse_template(template, pattern) 322 return sre_parse.expand_template(template, match) 323 324 def _subx(pattern, template): 325 # internal: pattern.sub/subn implementation helper 326 template = _compile_repl(template, pattern) 327 if not template[0] and len(template[1]) == 1: 328 # literal replacement 329 return template[1][0] 330 def filter(match, template=template): 331 return sre_parse.expand_template(template, match) 332 return filter 333 334 # register myself for pickling 335 336 import copyreg 337 338 def _pickle(p): 339 return _compile, (p.pattern, p.flags) 340 341 copyreg.pickle(_pattern_type, _pickle, _compile) 342 343 # -------------------------------------------------------------------- 344 # experimental stuff (see python-dev discussions for details) 345 346 class Scanner: 347 def __init__(self, lexicon, flags=0): 348 from sre_constants import BRANCH, SUBPATTERN 349 self.lexicon = lexicon 350 # combine phrases into a compound pattern 351 p = [] 352 s = sre_parse.Pattern() 353 s.flags = flags 354 for phrase, action in lexicon: 355 gid = s.opengroup() 356 p.append(sre_parse.SubPattern(s, [ 357 (SUBPATTERN, (gid, 0, 0, sre_parse.parse(phrase, flags))), 358 ])) 359 s.closegroup(gid, p[-1]) 360 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))]) 361 self.scanner = sre_compile.compile(p) 362 def scan(self, string): 363 result = [] 364 append = result.append 365 match = self.scanner.scanner(string).match 366 i = 0 367 while True: 368 m = match() 369 if not m: 370 break 371 j = m.end() 372 if i == j: 373 break 374 action = self.lexicon[m.lastindex-1][1] 375 if callable(action): 376 self.match = m 377 action = action(self, m.group()) 378 if action is not None: 379 append(action) 380 i = j 381 return result, string[i:]