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:]