Module re
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Source Code for Module re

  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 _alphanum = {} 192 for c in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890': 193 _alphanum[c] = 1 194 del c 195
196 -def escape(pattern):
197 "Escape all non-alphanumeric characters in pattern." 198 s = list(pattern) 199 alphanum = _alphanum 200 for i in range(len(pattern)): 201 c = pattern[i] 202 if c not in alphanum: 203 if c == "\000": 204 s[i] = "\\000" 205 else: 206 s[i] = "\\" + c 207 return pattern[:0].join(s)
208 209 # -------------------------------------------------------------------- 210 # internals 211 212 _cache = {} 213 _cache_repl = {} 214 215 _pattern_type = type(sre_compile.compile("", 0)) 216 217 _MAXCACHE = 100 218
219 -def _compile(*key):
220 # internal: compile pattern 221 cachekey = (type(key[0]),) + key 222 p = _cache.get(cachekey) 223 if p is not None: 224 return p 225 pattern, flags = key 226 if isinstance(pattern, _pattern_type): 227 return pattern 228 if not sre_compile.isstring(pattern): 229 raise TypeError, "first argument must be string or compiled pattern" 230 try: 231 p = sre_compile.compile(pattern, flags) 232 except error, v: 233 raise error, v # invalid expression 234 if len(_cache) >= _MAXCACHE: 235 _cache.clear() 236 _cache[cachekey] = p 237 return p
238
239 -def _compile_repl(*key):
240 # internal: compile replacement pattern 241 p = _cache_repl.get(key) 242 if p is not None: 243 return p 244 repl, pattern = key 245 try: 246 p = sre_parse.parse_template(repl, pattern) 247 except error, v: 248 raise error, v # invalid expression 249 if len(_cache_repl) >= _MAXCACHE: 250 _cache_repl.clear() 251 _cache_repl[key] = p 252 return p
253
254 -def _expand(pattern, match, template):
255 # internal: match.expand implementation hook 256 template = sre_parse.parse_template(template, pattern) 257 return sre_parse.expand_template(template, match)
258
259 -def _subx(pattern, template):
260 # internal: pattern.sub/subn implementation helper 261 template = _compile_repl(template, pattern) 262 if not template[0] and len(template[1]) == 1: 263 # literal replacement 264 return template[1][0] 265 def filter(match, template=template): 266 return sre_parse.expand_template(template, match)
267 return filter 268 269 # register myself for pickling 270 271 import copy_reg 272
273 -def _pickle(p):
274 return _compile, (p.pattern, p.flags)
275 276 copy_reg.pickle(_pattern_type, _pickle, _compile) 277 278 # -------------------------------------------------------------------- 279 # experimental stuff (see python-dev discussions for details) 280
281 -class Scanner:
282 - def __init__(self, lexicon, flags=0):
283 from sre_constants import BRANCH, SUBPATTERN 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 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))]) 294 s.groups = len(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 callable(action): 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:]
316