2 # Secret Labs' Regular Expression Engine
4 # re-compatible interface for the sre matching engine
6 # Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
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).
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.
17 r
"""Support for regular expressions (RE).
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.
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'.
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.
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.
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.
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.
100 This module also defines an exception 'error'.
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",
114 __version__
= "2.2.1"
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
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
129 error
= sre_compile
.error
131 # --------------------------------------------------------------------
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
)
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
)
144 def sub(pattern
, repl
, string
, count
=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 callable, it's passed the match object and must return
149 a replacement string to be used."""
150 return _compile(pattern
, 0).sub(repl
, string
, count
)
152 def subn(pattern
, repl
, string
, count
=0):
153 """Return a 2-tuple containing (new_string, number).
154 new_string is the string obtained by replacing the leftmost
155 non-overlapping occurrences of the pattern in the source
156 string by the replacement repl. number is the number of
157 substitutions that were made. repl can be either a string or a
158 callable; if a callable, it's passed the match object and must
159 return a replacement string to be used."""
160 return _compile(pattern
, 0).subn(repl
, string
, count
)
162 def split(pattern
, string
, maxsplit
=0):
163 """Split the source string by the occurrences of the pattern,
164 returning a list containing the resulting substrings."""
165 return _compile(pattern
, 0).split(string
, maxsplit
)
167 def findall(pattern
, string
, flags
=0):
168 """Return a list of all non-overlapping matches in the string.
170 If one or more groups are present in the pattern, return a
171 list of groups; this will be a list of tuples if the pattern
172 has more than one group.
174 Empty matches are included in the result."""
175 return _compile(pattern
, flags
).findall(string
)
177 if sys
.hexversion
>= 0x02020000:
178 __all__
.append("finditer")
179 def finditer(pattern
, string
, flags
=0):
180 """Return an iterator over all non-overlapping matches in the
181 string. For each match, the iterator returns a match object.
183 Empty matches are included in the result."""
184 return _compile(pattern
, flags
).finditer(string
)
186 def compile(pattern
, flags
=0):
187 "Compile a regular expression pattern, returning a pattern object."
188 return _compile(pattern
, flags
)
191 "Clear the regular expression cache"
195 def template(pattern
, flags
=0):
196 "Compile a template pattern, returning a pattern object"
197 return _compile(pattern
, flags|T
)
200 for c
in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890':
205 "Escape all non-alphanumeric characters in pattern."
208 for i
in range(len(pattern
)):
210 if c
not in alphanum
:
215 return pattern
[:0].join(s
)
217 # --------------------------------------------------------------------
223 _pattern_type
= type(sre_compile
.compile("", 0))
228 # internal: compile pattern
229 cachekey
= (type(key
[0]),) + key
230 p
= _cache
.get(cachekey
)
234 if isinstance(pattern
, _pattern_type
):
236 raise ValueError('Cannot process flags argument with a compiled pattern')
238 if not sre_compile
.isstring(pattern
):
239 raise TypeError, "first argument must be string or compiled pattern"
241 p
= sre_compile
.compile(pattern
, flags
)
243 raise error
, v
# invalid expression
244 if len(_cache
) >= _MAXCACHE
:
249 def _compile_repl(*key
):
250 # internal: compile replacement pattern
251 p
= _cache_repl
.get(key
)
256 p
= sre_parse
.parse_template(repl
, pattern
)
258 raise error
, v
# invalid expression
259 if len(_cache_repl
) >= _MAXCACHE
:
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
)
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
)
279 # register myself for pickling
284 return _compile
, (p
.pattern
, p
.flags
)
286 copy_reg
.pickle(_pattern_type
, _pickle
, _compile
)
288 # --------------------------------------------------------------------
289 # experimental stuff (see python-dev discussions for details)
292 def __init__(self
, lexicon
, flags
=0):
293 from sre_constants
import BRANCH
, SUBPATTERN
294 self
.lexicon
= lexicon
295 # combine phrases into a compound pattern
297 s
= sre_parse
.Pattern()
299 for phrase
, action
in lexicon
:
300 p
.append(sre_parse
.SubPattern(s
, [
301 (SUBPATTERN
, (len(p
)+1, sre_parse
.parse(phrase
, flags
))),
304 p
= sre_parse
.SubPattern(s
, [(BRANCH
, (None, p
))])
305 self
.scanner
= sre_compile
.compile(p
)
306 def scan(self
, string
):
308 append
= result
.append
309 match
= self
.scanner
.scanner(string
).match
318 action
= self
.lexicon
[m
.lastindex
-1][1]
321 action
= action(self
, m
.group())
322 if action
is not None:
325 return result
, string
[i
:]