sre

Source Code for Module sre

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. 33 "*" Matches 0 or more (greedy) repetitions of the preceding RE. 34 Greedy means that it will match as many repetitions as possible. 35 "+" Matches 1 or more (greedy) repetitions of the preceding RE. 36 "?" Matches 0 or 1 (greedy) of the preceding RE. 37 *?,+?,?? Non-greedy versions of the previous three special characters. 38 {m,n} Matches from m to n repetitions of the preceding RE. 39 {m,n}? Non-greedy version of the above. 40 "\\" Either escapes special characters or signals a special sequence. 41 [] Indicates a set of characters. 42 A "^" as the first character indicates a complementing set. 43 "|" A|B, creates an RE that will match either A or B. 44 (...) Matches the RE inside the parentheses. 45 The contents can be retrieved or matched later in the string. 46 (?iLmsux) Set the I, L, M, S, U, or X flag for the RE (see below). 47 (?:...) Non-grouping version of regular parentheses. 48 (?P<name>...) The substring matched by the group is accessible by name. 49 (?P=name) Matches the text matched earlier by the group named name. 50 (?#...) A comment; ignored. 51 (?=...) Matches if ... matches next, but doesn't consume the string. 52 (?!...) Matches if ... doesn't match next. 53 54 The special sequences consist of "\\" and a character from the list 55 below. If the ordinary character is not on the list, then the 56 resulting RE will match the second character. 57 \number Matches the contents of the group of the same number. 58 \A Matches only at the start of the string. 59 \Z Matches only at the end of the string. 60 \b Matches the empty string, but only at the start or end of a word. 61 \B Matches the empty string, but not at the start or end of a word. 62 \d Matches any decimal digit; equivalent to the set [0-9]. 63 \D Matches any non-digit character; equivalent to the set [^0-9]. 64 \s Matches any whitespace character; equivalent to [ \t\n\r\f\v]. 65 \S Matches any non-whitespace character; equiv. to [^ \t\n\r\f\v]. 66 \w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_]. 67 With LOCALE, it will match the set [0-9_] plus characters defined 68 as letters for the current locale. 69 \W Matches the complement of \w. 70 \\ Matches a literal backslash. 71 72 This module exports the following functions: 73 match Match a regular expression pattern to the beginning of a string. 74 search Search a string for the presence of a pattern. 75 sub Substitute occurrences of a pattern found in a string. 76 subn Same as sub, but also return the number of substitutions made. 77 split Split a string by the occurrences of a pattern. 78 findall Find all occurrences of a pattern in a string. 79 compile Compile a pattern into a RegexObject. 80 purge Clear the regular expression cache. 81 escape Backslash all non-alphanumerics in a string. 82 83 Some of the functions in this module takes flags as optional parameters: 84 I IGNORECASE Perform case-insensitive matching. 85 L LOCALE Make \w, \W, \b, \B, dependent on the current locale. 86 M MULTILINE "^" matches the beginning of lines as well as the string. 87 "$" matches the end of lines as well as the string. 88 S DOTALL "." matches any character at all, including the newline. 89 X VERBOSE Ignore whitespace and comments for nicer looking RE's. 90 U UNICODE Make \w, \W, \b, \B, dependent on the Unicode locale. 91 92 This module also defines an exception 'error'. 93 94 """ 95 96 import sys 97 import sre_compile 98 import sre_parse 99 100 # public symbols 101 __all__ = [ "match", "search", "sub", "subn", "split", "findall", 102 "compile", "purge", "template", "escape", "I", "L", "M", "S", "X", 103 "U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE", 104 "UNICODE", "error" ] 105 106 __version__ = "2.2.1" 107 108 # flags 109 I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case 110 L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale 111 U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale 112 M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline 113 S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline 114 X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments 115 116 # sre extensions (experimental, don't rely on these) 117 T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking 118 DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation 119 120 # sre exception 121 error = sre_compile.error 122 123 # -------------------------------------------------------------------- 124 # public interface 125

126 -def match(pattern, string, flags=0):

127 """Try to apply the pattern at the start of the string, returning 128 a match object, or None if no match was found.""" 129 return _compile(pattern, flags).match(string)

130

131 -def search(pattern, string, flags=0):

132 """Scan through string looking for a match to the pattern, returning 133 a match object, or None if no match was found.""" 134 return _compile(pattern, flags).search(string)

135

136 -def sub(pattern, repl, string, count=0):

137 """Return the string obtained by replacing the leftmost 138 non-overlapping occurrences of the pattern in string by the 139 replacement repl. repl can be either a string or a callable; 140 if a callable, it's passed the match object and must return 141 a replacement string to be used.""" 142 return _compile(pattern, 0).sub(repl, string, count)

143

144 -def subn(pattern, repl, string, count=0):

145 """Return a 2-tuple containing (new_string, number). 146 new_string is the string obtained by replacing the leftmost 147 non-overlapping occurrences of the pattern in the source 148 string by the replacement repl. number is the number of 149 substitutions that were made. repl can be either a string or a 150 callable; if a callable, it's passed the match object and must 151 return a replacement string to be used.""" 152 return _compile(pattern, 0).subn(repl, string, count)

153

154 -def split(pattern, string, maxsplit=0):

155 """Split the source string by the occurrences of the pattern, 156 returning a list containing the resulting substrings.""" 157 return _compile(pattern, 0).split(string, maxsplit)

158

159 -def findall(pattern, string, flags=0):

160 """Return a list of all non-overlapping matches in the string. 161 162 If one or more groups are present in the pattern, return a 163 list of groups; this will be a list of tuples if the pattern 164 has more than one group. 165 166 Empty matches are included in the result.""" 167 return _compile(pattern, flags).findall(string)

168 169 if sys.hexversion >= 0x02020000: 170 __all__.append("finditer")

171 - def finditer(pattern, string, flags=0):

172 """Return an iterator over all non-overlapping matches in the 173 string. For each match, the iterator returns a match object. 174 175 Empty matches are included in the result.""" 176 return _compile(pattern, flags).finditer(string)

177

178 -def compile(pattern, flags=0):

179 "Compile a regular expression pattern, returning a pattern object." 180 return _compile(pattern, flags)

181

182 -def purge():

183 "Clear the regular expression cache" 184 _cache.clear() 185 _cache_repl.clear()

186

187 -def template(pattern, flags=0):

188 "Compile a template pattern, returning a pattern object" 189 return _compile(pattern, flags|T)

190

191 -def escape(pattern):

192 "Escape all non-alphanumeric characters in pattern." 193 s = list(pattern) 194 for i in range(len(pattern)): 195 c = pattern[i] 196 if not ("a" <= c <= "z" or "A" <= c <= "Z" or "0" <= c <= "9"): 197 if c == "\000": 198 s[i] = "\\000" 199 else: 200 s[i] = "\\" + c 201 return pattern[:0].join(s)

202 203 # -------------------------------------------------------------------- 204 # internals 205 206 _cache = {} 207 _cache_repl = {} 208 209 _pattern_type = type(sre_compile.compile("", 0)) 210 211 _MAXCACHE = 100 212

213 -def _compile(*key):

214 # internal: compile pattern 215 cachekey = (type(key[0]),) + key 216 p = _cache.get(cachekey) 217 if p is not None: 218 return p 219 pattern, flags = key 220 if isinstance(pattern, _pattern_type): 221 return pattern 222 if not sre_compile.isstring(pattern): 223 raise TypeError, "first argument must be string or compiled pattern" 224 try: 225 p = sre_compile.compile(pattern, flags) 226 except error, v: 227 raise error, v # invalid expression 228 if len(_cache) >= _MAXCACHE: 229 _cache.clear() 230 _cache[cachekey] = p 231 return p

232

233 -def _compile_repl(*key):

234 # internal: compile replacement pattern 235 p = _cache_repl.get(key) 236 if p is not None: 237 return p 238 repl, pattern = key 239 try: 240 p = sre_parse.parse_template(repl, pattern) 241 except error, v: 242 raise error, v # invalid expression 243 if len(_cache_repl) >= _MAXCACHE: 244 _cache_repl.clear() 245 _cache_repl[key] = p 246 return p

247

248 -def _expand(pattern, match, template):

249 # internal: match.expand implementation hook 250 template = sre_parse.parse_template(template, pattern) 251 return sre_parse.expand_template(template, match)

252

253 -def _subx(pattern, template):

254 # internal: pattern.sub/subn implementation helper 255 template = _compile_repl(template, pattern) 256 if not template[0] and len(template[1]) == 1: 257 # literal replacement 258 return template[1][0] 259 def filter(match, template=template): 260 return sre_parse.expand_template(template, match)

261 return filter 262 263 # register myself for pickling 264 265 import copy_reg 266

267 -def _pickle(p):

268 return _compile, (p.pattern, p.flags)

269 270 copy_reg.pickle(_pattern_type, _pickle, _compile) 271 272 # -------------------------------------------------------------------- 273 # experimental stuff (see python-dev discussions for details) 274

275 -class Scanner:

276 - def __init__(self, lexicon, flags=0):

277 from sre_constants import BRANCH, SUBPATTERN 278 self.lexicon = lexicon 279 # combine phrases into a compound pattern 280 p = [] 281 s = sre_parse.Pattern() 282 s.flags = flags 283 for phrase, action in lexicon: 284 p.append(sre_parse.SubPattern(s, [ 285 (SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))), 286 ])) 287 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))]) 288 s.groups = len(p) 289 self.scanner = sre_compile.compile(p)

290 - def scan(self, string):

291 result = [] 292 append = result.append 293 match = self.scanner.scanner(string).match 294 i = 0 295 while 1: 296 m = match() 297 if not m: 298 break 299 j = m.end() 300 if i == j: 301 break 302 action = self.lexicon[m.lastindex-1][1] 303 if callable(action): 304 self.match = m 305 action = action(self, m.group()) 306 if action is not None: 307 append(action) 308 i = j 309 return result, string[i:]

310