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 (at] 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 import sys 105 import sre_compile 106 import sre_parse 107 108 # public symbols 109 __all__ = [ "match", "search", "sub", "subn", "split", "findall", 110 "compile", "purge", "template", "escape", "I", "L", "M", "S", "X", 111 "U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE", 112 "UNICODE", "error" ] 113 114 __version__ = "2.2.1" 115 116 # flags 117 I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case 118 L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale 119 U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale 120 M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline 121 S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline 122 X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments 123 124 # sre extensions (experimental, don't rely on these) 125 T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking 126 DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation 127 128 # sre exception 129 error = sre_compile.error 130 131 # -------------------------------------------------------------------- 132 # public interface 133 134 def match(pattern, string, flags=0): 135 """Try to apply the pattern at the start of the string, returning 136 a match object, or None if no match was found.""" 137 return _compile(pattern, flags).match(string) 138 139 def search(pattern, string, flags=0): 140 """Scan through string looking for a match to the pattern, returning 141 a match object, or None if no match was found.""" 142 return _compile(pattern, flags).search(string) 143 144 def sub(pattern, repl, string, count=0, flags=0): 145 """Return the string obtained by replacing the leftmost 146 non-overlapping occurrences of the pattern in string by the 147 replacement repl. repl can be either a string or a callable; 148 if a string, backslash escapes in it are processed. If it is 149 a callable, it's passed the match object and must return 150 a replacement string to be used.""" 151 return _compile(pattern, flags).sub(repl, string, count) 152 153 def subn(pattern, repl, string, count=0, flags=0): 154 """Return a 2-tuple containing (new_string, number). 155 new_string is the string obtained by replacing the leftmost 156 non-overlapping occurrences of the pattern in the source 157 string by the replacement repl. number is the number of 158 substitutions that were made. repl can be either a string or a 159 callable; if a string, backslash escapes in it are processed. 160 If it is a callable, it's passed the match object and must 161 return a replacement string to be used.""" 162 return _compile(pattern, flags).subn(repl, string, count) 163 164 def split(pattern, string, maxsplit=0, flags=0): 165 """Split the source string by the occurrences of the pattern, 166 returning a list containing the resulting substrings.""" 167 return _compile(pattern, flags).split(string, maxsplit) 168 169 def findall(pattern, string, flags=0): 170 """Return a list of all non-overlapping matches in the string. 171 172 If one or more groups are present in the pattern, return a 173 list of groups; this will be a list of tuples if the pattern 174 has more than one group. 175 176 Empty matches are included in the result.""" 177 return _compile(pattern, flags).findall(string) 178 179 if sys.hexversion >= 0x02020000: 180 __all__.append("finditer") 181 def finditer(pattern, string, flags=0): 182 """Return an iterator over all non-overlapping matches in the 183 string. For each match, the iterator returns a match object. 184 185 Empty matches are included in the result.""" 186 return _compile(pattern, flags).finditer(string) 187 188 def compile(pattern, flags=0): 189 "Compile a regular expression pattern, returning a pattern object." 190 return _compile(pattern, flags) 191 192 def purge(): 193 "Clear the regular expression cache" 194 _cache.clear() 195 _cache_repl.clear() 196 197 def template(pattern, flags=0): 198 "Compile a template pattern, returning a pattern object" 199 return _compile(pattern, flags|T) 200 201 _alphanum = {} 202 for c in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890': 203 _alphanum[c] = 1 204 del c 205 206 def escape(pattern): 207 "Escape all non-alphanumeric characters in pattern." 208 s = list(pattern) 209 alphanum = _alphanum 210 for i, c in enumerate(pattern): 211 if c not in alphanum: 212 if c == "\000": 213 s[i] = "\\000" 214 else: 215 s[i] = "\\" + c 216 return pattern[:0].join(s) 217 218 # -------------------------------------------------------------------- 219 # internals 220 221 _cache = {} 222 _cache_repl = {} 223 224 _pattern_type = type(sre_compile.compile("", 0)) 225 226 _MAXCACHE = 100 227 228 def _compile(*key): 229 # internal: compile pattern 230 cachekey = (type(key[0]),) + key 231 p = _cache.get(cachekey) 232 if p is not None: 233 return p 234 pattern, flags = key 235 if isinstance(pattern, _pattern_type): 236 if flags: 237 raise ValueError('Cannot process flags argument with a compiled pattern') 238 return pattern 239 if not sre_compile.isstring(pattern): 240 raise TypeError, "first argument must be string or compiled pattern" 241 try: 242 p = sre_compile.compile(pattern, flags) 243 except error, v: 244 raise error, v # invalid expression 245 if len(_cache) >= _MAXCACHE: 246 _cache.clear() 247 _cache[cachekey] = p 248 return p 249 250 def _compile_repl(*key): 251 # internal: compile replacement pattern 252 p = _cache_repl.get(key) 253 if p is not None: 254 return p 255 repl, pattern = key 256 try: 257 p = sre_parse.parse_template(repl, pattern) 258 except error, v: 259 raise error, v # invalid expression 260 if len(_cache_repl) >= _MAXCACHE: 261 _cache_repl.clear() 262 _cache_repl[key] = p 263 return p 264 265 def _expand(pattern, match, template): 266 # internal: match.expand implementation hook 267 template = sre_parse.parse_template(template, pattern) 268 return sre_parse.expand_template(template, match) 269 270 def _subx(pattern, template): 271 # internal: pattern.sub/subn implementation helper 272 template = _compile_repl(template, pattern) 273 if not template[0] and len(template[1]) == 1: 274 # literal replacement 275 return template[1][0] 276 def filter(match, template=template): 277 return sre_parse.expand_template(template, match) 278 return filter 279 280 # register myself for pickling 281 282 import copy_reg 283 284 def _pickle(p): 285 return _compile, (p.pattern, p.flags) 286 287 copy_reg.pickle(_pattern_type, _pickle, _compile) 288 289 # -------------------------------------------------------------------- 290 # experimental stuff (see python-dev discussions for details) 291 292 class Scanner: 293 def __init__(self, lexicon, flags=0): 294 from sre_constants import BRANCH, SUBPATTERN 295 self.lexicon = lexicon 296 # combine phrases into a compound pattern 297 p = [] 298 s = sre_parse.Pattern() 299 s.flags = flags 300 for phrase, action in lexicon: 301 p.append(sre_parse.SubPattern(s, [ 302 (SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))), 303 ])) 304 s.groups = len(p)+1 305 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))]) 306 self.scanner = sre_compile.compile(p) 307 def scan(self, string): 308 result = [] 309 append = result.append 310 match = self.scanner.scanner(string).match 311 i = 0 312 while 1: 313 m = match() 314 if not m: 315 break 316 j = m.end() 317 if i == j: 318 break 319 action = self.lexicon[m.lastindex-1][1] 320 if hasattr(action, '__call__'): 321 self.match = m 322 action = action(self, m.group()) 323 if action is not None: 324 append(action) 325 i = j 326 return result, string[i:] 327