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 ([email protected]). 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 17r"""Support for regular expressions (RE). 18 19This module provides regular expression matching operations similar to 20those found in Perl. It supports both 8-bit and Unicode strings; both 21the pattern and the strings being processed can contain null bytes and 22characters outside the US ASCII range. 23 24Regular expressions can contain both special and ordinary characters. 25Most ordinary characters, like "A", "a", or "0", are the simplest 26regular expressions; they simply match themselves. You can 27concatenate ordinary characters, so last matches the string 'last'. 28 29The 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) The letters set the corresponding flags defined 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 59The special sequences consist of "\\" and a character from the list 60below. If the ordinary character is not on the list, then the 61resulting 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] 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 [ \t\n\r\f\v] 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 87This 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 Pattern object. 97 purge Clear the regular expression cache. 98 escape Backslash all non-alphanumerics in a string. 99 100Each function other than purge and escape can take an optional 'flags' argument 101consisting of one or more of the following module constants, joined by "|". 102A, L, and U are mutually exclusive. 103 A ASCII For string patterns, make \w, \W, \b, \B, \d, \D 104 match the corresponding ASCII character categories 105 (rather than the whole Unicode categories, which is the 106 default). 107 For bytes patterns, this flag is the only available 108 behaviour and needn't be specified. 109 I IGNORECASE Perform case-insensitive matching. 110 L LOCALE Make \w, \W, \b, \B, dependent on the current locale. 111 M MULTILINE "^" matches the beginning of lines (after a newline) 112 as well as the string. 113 "$" matches the end of lines (before a newline) as well 114 as the end of the string. 115 S DOTALL "." matches any character at all, including the newline. 116 X VERBOSE Ignore whitespace and comments for nicer looking RE's. 117 U UNICODE For compatibility only. Ignored for string patterns (it 118 is the default), and forbidden for bytes patterns. 119 120This module also defines an exception 'error'. 121 122""" 123 124import enum 125from . import _compiler, _parser 126import functools 127 128 129# public symbols 130__all__ = [ 131 "match", "fullmatch", "search", "sub", "subn", "split", 132 "findall", "finditer", "compile", "purge", "template", "escape", 133 "error", "Pattern", "Match", "A", "I", "L", "M", "S", "X", "U", 134 "ASCII", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE", 135 "UNICODE", "NOFLAG", "RegexFlag", 136] 137 138__version__ = "2.2.1" 139 140@enum.global_enum 141@enum._simple_enum(enum.IntFlag, boundary=enum.KEEP) 142class RegexFlag: 143 NOFLAG = 0 144 ASCII = A = _compiler.SRE_FLAG_ASCII # assume ascii "locale" 145 IGNORECASE = I = _compiler.SRE_FLAG_IGNORECASE # ignore case 146 LOCALE = L = _compiler.SRE_FLAG_LOCALE # assume current 8-bit locale 147 UNICODE = U = _compiler.SRE_FLAG_UNICODE # assume unicode "locale" 148 MULTILINE = M = _compiler.SRE_FLAG_MULTILINE # make anchors look for newline 149 DOTALL = S = _compiler.SRE_FLAG_DOTALL # make dot match newline 150 VERBOSE = X = _compiler.SRE_FLAG_VERBOSE # ignore whitespace and comments 151 # sre extensions (experimental, don't rely on these) 152 TEMPLATE = T = _compiler.SRE_FLAG_TEMPLATE # unknown purpose, deprecated 153 DEBUG = _compiler.SRE_FLAG_DEBUG # dump pattern after compilation 154 __str__ = object.__str__ 155 _numeric_repr_ = hex 156 157# sre exception 158error = _compiler.error 159 160# -------------------------------------------------------------------- 161# public interface 162 163def match(pattern, string, flags=0): 164 """Try to apply the pattern at the start of the string, returning 165 a Match object, or None if no match was found.""" 166 return _compile(pattern, flags).match(string) 167 168def fullmatch(pattern, string, flags=0): 169 """Try to apply the pattern to all of the string, returning 170 a Match object, or None if no match was found.""" 171 return _compile(pattern, flags).fullmatch(string) 172 173def search(pattern, string, flags=0): 174 """Scan through string looking for a match to the pattern, returning 175 a Match object, or None if no match was found.""" 176 return _compile(pattern, flags).search(string) 177 178def sub(pattern, repl, string, count=0, flags=0): 179 """Return the string obtained by replacing the leftmost 180 non-overlapping occurrences of the pattern in string by the 181 replacement repl. repl can be either a string or a callable; 182 if a string, backslash escapes in it are processed. If it is 183 a callable, it's passed the Match object and must return 184 a replacement string to be used.""" 185 return _compile(pattern, flags).sub(repl, string, count) 186 187def subn(pattern, repl, string, count=0, flags=0): 188 """Return a 2-tuple containing (new_string, number). 189 new_string is the string obtained by replacing the leftmost 190 non-overlapping occurrences of the pattern in the source 191 string by the replacement repl. number is the number of 192 substitutions that were made. repl can be either a string or a 193 callable; if a string, backslash escapes in it are processed. 194 If it is a callable, it's passed the Match object and must 195 return a replacement string to be used.""" 196 return _compile(pattern, flags).subn(repl, string, count) 197 198def split(pattern, string, maxsplit=0, flags=0): 199 """Split the source string by the occurrences of the pattern, 200 returning a list containing the resulting substrings. If 201 capturing parentheses are used in pattern, then the text of all 202 groups in the pattern are also returned as part of the resulting 203 list. If maxsplit is nonzero, at most maxsplit splits occur, 204 and the remainder of the string is returned as the final element 205 of the list.""" 206 return _compile(pattern, flags).split(string, maxsplit) 207 208def findall(pattern, string, flags=0): 209 """Return a list of all non-overlapping matches in the string. 210 211 If one or more capturing groups are present in the pattern, return 212 a list of groups; this will be a list of tuples if the pattern 213 has more than one group. 214 215 Empty matches are included in the result.""" 216 return _compile(pattern, flags).findall(string) 217 218def finditer(pattern, string, flags=0): 219 """Return an iterator over all non-overlapping matches in the 220 string. For each match, the iterator returns a Match object. 221 222 Empty matches are included in the result.""" 223 return _compile(pattern, flags).finditer(string) 224 225def compile(pattern, flags=0): 226 "Compile a regular expression pattern, returning a Pattern object." 227 return _compile(pattern, flags) 228 229def purge(): 230 "Clear the regular expression caches" 231 _cache.clear() 232 _compile_repl.cache_clear() 233 234def template(pattern, flags=0): 235 "Compile a template pattern, returning a Pattern object, deprecated" 236 import warnings 237 warnings.warn("The re.template() function is deprecated " 238 "as it is an undocumented function " 239 "without an obvious purpose. " 240 "Use re.compile() instead.", 241 DeprecationWarning) 242 with warnings.catch_warnings(): 243 warnings.simplefilter("ignore", DeprecationWarning) # warn just once 244 return _compile(pattern, flags|T) 245 246# SPECIAL_CHARS 247# closing ')', '}' and ']' 248# '-' (a range in character set) 249# '&', '~', (extended character set operations) 250# '#' (comment) and WHITESPACE (ignored) in verbose mode 251_special_chars_map = {i: '\\' + chr(i) for i in b'()[]{}?*+-|^$\\.&~# \t\n\r\v\f'} 252 253def escape(pattern): 254 """ 255 Escape special characters in a string. 256 """ 257 if isinstance(pattern, str): 258 return pattern.translate(_special_chars_map) 259 else: 260 pattern = str(pattern, 'latin1') 261 return pattern.translate(_special_chars_map).encode('latin1') 262 263Pattern = type(_compiler.compile('', 0)) 264Match = type(_compiler.compile('', 0).match('')) 265 266# -------------------------------------------------------------------- 267# internals 268 269_cache = {} # ordered! 270 271_MAXCACHE = 512 272def _compile(pattern, flags): 273 # internal: compile pattern 274 if isinstance(flags, RegexFlag): 275 flags = flags.value 276 try: 277 return _cache[type(pattern), pattern, flags] 278 except KeyError: 279 pass 280 if isinstance(pattern, Pattern): 281 if flags: 282 raise ValueError( 283 "cannot process flags argument with a compiled pattern") 284 return pattern 285 if not _compiler.isstring(pattern): 286 raise TypeError("first argument must be string or compiled pattern") 287 if flags & T: 288 import warnings 289 warnings.warn("The re.TEMPLATE/re.T flag is deprecated " 290 "as it is an undocumented flag " 291 "without an obvious purpose. " 292 "Don't use it.", 293 DeprecationWarning) 294 p = _compiler.compile(pattern, flags) 295 if not (flags & DEBUG): 296 if len(_cache) >= _MAXCACHE: 297 # Drop the oldest item 298 try: 299 del _cache[next(iter(_cache))] 300 except (StopIteration, RuntimeError, KeyError): 301 pass 302 _cache[type(pattern), pattern, flags] = p 303 return p 304 305@functools.lru_cache(_MAXCACHE) 306def _compile_repl(repl, pattern): 307 # internal: compile replacement pattern 308 return _parser.parse_template(repl, pattern) 309 310def _expand(pattern, match, template): 311 # internal: Match.expand implementation hook 312 template = _parser.parse_template(template, pattern) 313 return _parser.expand_template(template, match) 314 315def _subx(pattern, template): 316 # internal: Pattern.sub/subn implementation helper 317 template = _compile_repl(template, pattern) 318 if not template[0] and len(template[1]) == 1: 319 # literal replacement 320 return template[1][0] 321 def filter(match, template=template): 322 return _parser.expand_template(template, match) 323 return filter 324 325# register myself for pickling 326 327import copyreg 328 329def _pickle(p): 330 return _compile, (p.pattern, p.flags) 331 332copyreg.pickle(Pattern, _pickle, _compile) 333 334# -------------------------------------------------------------------- 335# experimental stuff (see python-dev discussions for details) 336 337class Scanner: 338 def __init__(self, lexicon, flags=0): 339 from ._constants import BRANCH, SUBPATTERN 340 if isinstance(flags, RegexFlag): 341 flags = flags.value 342 self.lexicon = lexicon 343 # combine phrases into a compound pattern 344 p = [] 345 s = _parser.State() 346 s.flags = flags 347 for phrase, action in lexicon: 348 gid = s.opengroup() 349 p.append(_parser.SubPattern(s, [ 350 (SUBPATTERN, (gid, 0, 0, _parser.parse(phrase, flags))), 351 ])) 352 s.closegroup(gid, p[-1]) 353 p = _parser.SubPattern(s, [(BRANCH, (None, p))]) 354 self.scanner = _compiler.compile(p) 355 def scan(self, string): 356 result = [] 357 append = result.append 358 match = self.scanner.scanner(string).match 359 i = 0 360 while True: 361 m = match() 362 if not m: 363 break 364 j = m.end() 365 if i == j: 366 break 367 action = self.lexicon[m.lastindex-1][1] 368 if callable(action): 369 self.match = m 370 action = action(self, m.group()) 371 if action is not None: 372 append(action) 373 i = j 374 return result, string[i:] 375