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 = frozenset( 202 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789") 203 204 def escape(pattern): 205 "Escape all non-alphanumeric characters in pattern." 206 s = list(pattern) 207 alphanum = _alphanum 208 for i, c in enumerate(pattern): 209 if c not in alphanum: 210 if c == "\000": 211 s[i] = "\\000" 212 else: 213 s[i] = "\\" + c 214 return pattern[:0].join(s) 215 216 # -------------------------------------------------------------------- 217 # internals 218 219 _cache = {} 220 _cache_repl = {} 221 222 _pattern_type = type(sre_compile.compile("", 0)) 223 224 _MAXCACHE = 100 225 226 def _compile(*key): 227 # internal: compile pattern 228 cachekey = (type(key[0]),) + key 229 p = _cache.get(cachekey) 230 if p is not None: 231 return p 232 pattern, flags = key 233 if isinstance(pattern, _pattern_type): 234 if flags: 235 raise ValueError('Cannot process flags argument with a compiled pattern') 236 return pattern 237 if not sre_compile.isstring(pattern): 238 raise TypeError, "first argument must be string or compiled pattern" 239 try: 240 p = sre_compile.compile(pattern, flags) 241 except error, v: 242 raise error, v # invalid expression 243 if len(_cache) >= _MAXCACHE: 244 _cache.clear() 245 _cache[cachekey] = p 246 return p 247 248 def _compile_repl(*key): 249 # internal: compile replacement pattern 250 p = _cache_repl.get(key) 251 if p is not None: 252 return p 253 repl, pattern = key 254 try: 255 p = sre_parse.parse_template(repl, pattern) 256 except error, v: 257 raise error, v # invalid expression 258 if len(_cache_repl) >= _MAXCACHE: 259 _cache_repl.clear() 260 _cache_repl[key] = p 261 return p 262 263 def _expand(pattern, match, template): 264 # internal: match.expand implementation hook 265 template = sre_parse.parse_template(template, pattern) 266 return sre_parse.expand_template(template, match) 267 268 def _subx(pattern, template): 269 # internal: pattern.sub/subn implementation helper 270 template = _compile_repl(template, pattern) 271 if not template[0] and len(template[1]) == 1: 272 # literal replacement 273 return template[1][0] 274 def filter(match, template=template): 275 return sre_parse.expand_template(template, match) 276 return filter 277 278 # register myself for pickling 279 280 import copy_reg 281 282 def _pickle(p): 283 return _compile, (p.pattern, p.flags) 284 285 copy_reg.pickle(_pattern_type, _pickle, _compile) 286 287 # -------------------------------------------------------------------- 288 # experimental stuff (see python-dev discussions for details) 289 290 class Scanner: 291 def __init__(self, lexicon, flags=0): 292 from sre_constants import BRANCH, SUBPATTERN 293 self.lexicon = lexicon 294 # combine phrases into a compound pattern 295 p = [] 296 s = sre_parse.Pattern() 297 s.flags = flags 298 for phrase, action in lexicon: 299 p.append(sre_parse.SubPattern(s, [ 300 (SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))), 301 ])) 302 s.groups = len(p)+1 303 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))]) 304 self.scanner = sre_compile.compile(p) 305 def scan(self, string): 306 result = [] 307 append = result.append 308 match = self.scanner.scanner(string).match 309 i = 0 310 while 1: 311 m = match() 312 if not m: 313 break 314 j = m.end() 315 if i == j: 316 break 317 action = self.lexicon[m.lastindex-1][1] 318 if hasattr(action, '__call__'): 319 self.match = m 320 action = action(self, m.group()) 321 if action is not None: 322 append(action) 323 i = j 324 return result, string[i:] 325
