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.
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.
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.
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.
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.
92 This module also defines an exception 'error'.
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",
106 __version__
= "2.2.1"
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
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
121 error
= sre_compile
.error
123 # --------------------------------------------------------------------
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
)
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
)
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
)
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
)
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
)
159 def findall(pattern
, string
, flags
=0):
160 """Return a list of all non-overlapping matches in the string.
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.
166 Empty matches are included in the result."""
167 return _compile(pattern
, flags
).findall(string
)
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.
175 Empty matches are included in the result."""
176 return _compile(pattern
, flags
).finditer(string
)
178 def compile(pattern
, flags
=0):
179 "Compile a regular expression pattern, returning a pattern object."
180 return _compile(pattern
, flags
)
183 "Clear the regular expression cache"
187 def template(pattern
, flags
=0):
188 "Compile a template pattern, returning a pattern object"
189 return _compile(pattern
, flags|T
)
192 for c
in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890':
197 "Escape all non-alphanumeric characters in pattern."
200 for i
in range(len(pattern
)):
202 if c
not in alphanum
:
207 return pattern
[:0].join(s
)
209 # --------------------------------------------------------------------
215 _pattern_type
= type(sre_compile
.compile("", 0))
220 # internal: compile pattern
221 cachekey
= (type(key
[0]),) + key
222 p
= _cache
.get(cachekey
)
226 if isinstance(pattern
, _pattern_type
):
228 raise ValueError('Cannot process flags argument with a compiled pattern')
230 if not sre_compile
.isstring(pattern
):
231 raise TypeError, "first argument must be string or compiled pattern"
233 p
= sre_compile
.compile(pattern
, flags
)
235 raise error
, v
# invalid expression
236 if len(_cache
) >= _MAXCACHE
:
241 def _compile_repl(*key
):
242 # internal: compile replacement pattern
243 p
= _cache_repl
.get(key
)
248 p
= sre_parse
.parse_template(repl
, pattern
)
250 raise error
, v
# invalid expression
251 if len(_cache_repl
) >= _MAXCACHE
:
256 def _expand(pattern
, match
, template
):
257 # internal: match.expand implementation hook
258 template
= sre_parse
.parse_template(template
, pattern
)
259 return sre_parse
.expand_template(template
, match
)
261 def _subx(pattern
, template
):
262 # internal: pattern.sub/subn implementation helper
263 template
= _compile_repl(template
, pattern
)
264 if not template
[0] and len(template
[1]) == 1:
265 # literal replacement
266 return template
[1][0]
267 def filter(match
, template
=template
):
268 return sre_parse
.expand_template(template
, match
)
271 # register myself for pickling
276 return _compile
, (p
.pattern
, p
.flags
)
278 copy_reg
.pickle(_pattern_type
, _pickle
, _compile
)
280 # --------------------------------------------------------------------
281 # experimental stuff (see python-dev discussions for details)
284 def __init__(self
, lexicon
, flags
=0):
285 from sre_constants
import BRANCH
, SUBPATTERN
286 self
.lexicon
= lexicon
287 # combine phrases into a compound pattern
289 s
= sre_parse
.Pattern()
291 for phrase
, action
in lexicon
:
292 p
.append(sre_parse
.SubPattern(s
, [
293 (SUBPATTERN
, (len(p
)+1, sre_parse
.parse(phrase
, flags
))),
295 p
= sre_parse
.SubPattern(s
, [(BRANCH
, (None, p
))])
297 self
.scanner
= sre_compile
.compile(p
)
298 def scan(self
, string
):
300 append
= result
.append
301 match
= self
.scanner
.scanner(string
).match
310 action
= self
.lexicon
[m
.lastindex
-1][1]
313 action
= action(self
, m
.group())
314 if action
is not None:
317 return result
, string
[i
:]