mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-11-04 11:49:12 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 11
cpython/Lib/sre.py
Fred Drake 9f5b822fb3 Convert docstring to "raw" string.
2001-09-04 19:20:06 +00:00

348 lines
13 KiB
Python
Raw Blame History

#
# Secret Labs' Regular Expression Engine
#
# re-compatible interface for the sre matching engine
#
# Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
#
# This version of the SRE library can be redistributed under CNRI's
# Python 1.6 license. For any other use, please contact Secret Labs
# AB (info@pythonware.com).
#
# Portions of this engine have been developed in cooperation with
# CNRI. Hewlett-Packard provided funding for 1.6 integration and
# other compatibility work.
#
r"""Support for regular expressions (RE).
This module provides regular expression matching operations similar to
those found in Perl. It's 8-bit clean: the strings being processed may
contain both null bytes and characters whose high bit is set. Regular
expression pattern strings may not contain null bytes, but can specify
the null byte using the \\number notation. Characters with the high
bit set may be included.
Regular expressions can contain both special and ordinary
characters. Most ordinary characters, like "A", "a", or "0", are the
simplest regular expressions; they simply match themselves. You can
concatenate ordinary characters, so last matches the string 'last'.
The special characters are:
"." Matches any character except a newline.
"^" Matches the start of the string.
"$" Matches the end of the string.
"*" Matches 0 or more (greedy) repetitions of the preceding RE.
Greedy means that it will match as many repetitions as possible.
"+" Matches 1 or more (greedy) repetitions of the preceding RE.
"?" Matches 0 or 1 (greedy) of the preceding RE.
*?,+?,?? Non-greedy versions of the previous three special characters.
{m,n} Matches from m to n repetitions of the preceding RE.
{m,n}? Non-greedy version of the above.
"\\" Either escapes special characters or signals a special sequence.
[] Indicates a set of characters.
A "^" as the first character indicates a complementing set.
"|" A|B, creates an RE that will match either A or B.
(...) Matches the RE inside the parentheses.
The contents can be retrieved or matched later in the string.
(?iLmsx) Set the I, L, M, S, or X flag for the RE.
(?:...) Non-grouping version of regular parentheses.
(?P<name>...) The substring matched by the group is accessible by name.
(?P=name) Matches the text matched earlier by the group named name.
(?#...) A comment; ignored.
(?=...) Matches if ... matches next, but doesn't consume the string.
(?!...) Matches if ... doesn't match next.
The special sequences consist of "\\" and a character from the list
below. If the ordinary character is not on the list, then the
resulting RE will match the second character.
\number Matches the contents of the group of the same number.
\A Matches only at the start of the string.
\Z Matches only at the end of the string.
\b Matches the empty string, but only at the start or end of a word.
\B Matches the empty string, but not at the start or end of a word.
\d Matches any decimal digit; equivalent to the set [0-9].
\D Matches any non-digit character; equivalent to the set [^0-9].
\s Matches any whitespace character; equivalent to [ \t\n\r\f\v].
\S Matches any non-whitespace character; equiv. to [^ \t\n\r\f\v].
\w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_].
With LOCALE, it will match the set [0-9_] plus characters defined
as letters for the current locale.
\W Matches the complement of \w.
\\ Matches a literal backslash.
This module exports the following functions:
match Match a regular expression pattern to the beginning of a string.
search Search a string for the presence of a pattern.
sub Substitute occurrences of a pattern found in a string.
subn Same as sub, but also return the number of substitutions made.
split Split a string by the occurrences of a pattern.
findall Find all occurrences of a pattern in a string.
compile Compile a pattern into a RegexObject.
purge Clear the regular expression cache.
template Compile a template pattern, returning a pattern object.
escape Backslash all non-alphanumerics in a string.
Some of the functions in this module takes flags as optional parameters:
I IGNORECASE Perform case-insensitive matching.
L LOCALE Make \w, \W, \b, \B, dependent on the current locale.
M MULTILINE "^" matches the beginning of lines as well as the string.
"$" matches the end of lines as well as the string.
S DOTALL "." matches any character at all, including the newline.
X VERBOSE Ignore whitespace and comments for nicer looking RE's.
U UNICODE Use unicode locale.
This module also defines an exception 'error'.
"""
import sre_compile
import sre_parse
# public symbols
__all__ = [ "match", "search", "sub", "subn", "split", "findall",
"compile", "purge", "template", "escape", "I", "L", "M", "S", "X",
"U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
"UNICODE", "error" ]
__version__ = "2.1b2"
# this module works under 1.5.2 and later. don't use string methods
import string
# flags
I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case
L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale
M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline
X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments
# sre extensions (experimental, don't rely on these)
T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking
DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation
# sre exception
error = sre_compile.error
# --------------------------------------------------------------------
# public interface
def match(pattern, string, flags=0):
"""Try to apply the pattern at the start of the string, returning
a match object, or None if no match was found."""
return _compile(pattern, flags).match(string)
def search(pattern, string, flags=0):
"""Scan through string looking for a match to the pattern, returning
a match object, or None if no match was found."""
return _compile(pattern, flags).search(string)
def sub(pattern, repl, string, count=0):
"""Return the string obtained by replacing the leftmost
non-overlapping occurrences of the pattern in string by the
replacement repl"""
return _compile(pattern, 0).sub(repl, string, count)
def subn(pattern, repl, string, count=0):
"""Return a 2-tuple containing (new_string, number).
new_string is the string obtained by replacing the leftmost
non-overlapping occurrences of the pattern in the source
string by the replacement repl. number is the number of
substitutions that were made."""
return _compile(pattern, 0).subn(repl, string, count)
def split(pattern, string, maxsplit=0):
"""Split the source string by the occurrences of the pattern,
returning a list containing the resulting substrings."""
return _compile(pattern, 0).split(string, maxsplit)
def findall(pattern, string):
"""Return a list of all non-overlapping matches in the string.
If one or more groups are present in the pattern, return a
list of groups; this will be a list of tuples if the pattern
has more than one group.
Empty matches are included in the result."""
return _compile(pattern, 0).findall(string)
def compile(pattern, flags=0):
"Compile a regular expression pattern, returning a pattern object."
return _compile(pattern, flags)
def purge():
"Clear the regular expression cache"
_cache.clear()
_cache_repl.clear()
def template(pattern, flags=0):
"Compile a template pattern, returning a pattern object"
return _compile(pattern, flags|T)
def escape(pattern):
"Escape all non-alphanumeric characters in pattern."
s = list(pattern)
for i in range(len(pattern)):
c = pattern[i]
if not ("a" <= c <= "z" or "A" <= c <= "Z" or "0" <= c <= "9"):
if c == "\000":
s[i] = "\\000"
else:
s[i] = "\\" + c
return _join(s, pattern)
# --------------------------------------------------------------------
# internals
_cache = {}
_cache_repl = {}
_MAXCACHE = 100
def _join(seq, sep):
# internal: join into string having the same type as sep
return string.join(seq, sep[:0])
def _compile(*key):
# internal: compile pattern
p = _cache.get(key)
if p is not None:
return p
pattern, flags = key
if type(pattern) not in sre_compile.STRING_TYPES:
return pattern
try:
p = sre_compile.compile(pattern, flags)
except error, v:
raise error, v # invalid expression
if len(_cache) >= _MAXCACHE:
_cache.clear()
_cache[key] = p
return p
def _compile_repl(*key):
# internal: compile replacement pattern
p = _cache_repl.get(key)
if p is not None:
return p
repl, pattern = key
try:
p = sre_parse.parse_template(repl, pattern)
except error, v:
raise error, v # invalid expression
if len(_cache_repl) >= _MAXCACHE:
_cache_repl.clear()
_cache_repl[key] = p
return p
def _expand(pattern, match, template):
# internal: match.expand implementation hook
template = sre_parse.parse_template(template, pattern)
return sre_parse.expand_template(template, match)
def _sub(pattern, template, text, count=0):
# internal: pattern.sub implementation hook
return _subn(pattern, template, text, count, 1)[0]
def _subn(pattern, template, text, count=0, sub=0):
# internal: pattern.subn implementation hook
if callable(template):
filter = template
else:
template = _compile_repl(template, pattern)
literals = template[1]
sub = 0 # temporarly disabled, see bug #449000
if (sub and not count and pattern._isliteral() and
len(literals) == 1 and literals[0]):
# shortcut: both pattern and string are literals
return string.replace(text, pattern.pattern, literals[0]), 0
def filter(match, template=template):
return sre_parse.expand_template(template, match)
n = i = 0
s = []
append = s.append
c = pattern.scanner(text)
while not count or n < count:
m = c.search()
if not m:
break
b, e = m.span()
if i < b:
append(text[i:b])
append(filter(m))
i = e
n = n + 1
append(text[i:])
return _join(s, text[:0]), n
def _split(pattern, text, maxsplit=0):
# internal: pattern.split implementation hook
n = i = 0
s = []
append = s.append
extend = s.extend
c = pattern.scanner(text)
g = pattern.groups
while not maxsplit or n < maxsplit:
m = c.search()
if not m:
break
b, e = m.span()
if b == e:
if i >= len(text):
break
continue
append(text[i:b])
if g and b != e:
extend(list(m.groups()))
i = e
n = n + 1
append(text[i:])
return s
# register myself for pickling
import copy_reg
def _pickle(p):
return _compile, (p.pattern, p.flags)
copy_reg.pickle(type(_compile("", 0)), _pickle, _compile)
# --------------------------------------------------------------------
# experimental stuff (see python-dev discussions for details)
class Scanner:
def __init__(self, lexicon):
from sre_constants import BRANCH, SUBPATTERN
self.lexicon = lexicon
# combine phrases into a compound pattern
p = []
s = sre_parse.Pattern()
for phrase, action in lexicon:
p.append(sre_parse.SubPattern(s, [
(SUBPATTERN, (len(p), sre_parse.parse(phrase))),
]))
p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])
s.groups = len(p)
self.scanner = sre_compile.compile(p)
def scan(self, string):
result = []
append = result.append
match = self.scanner.match
i = 0
while 1:
m = match(string, i)
if not m:
break
j = m.end()
if i == j:
break
action = self.lexicon[m.lastindex][1]
if callable(action):
self.match = m
action = action(self, m.group())
if action is not None:
append(action)
i = j
return result, string[i:]
Reference in a new issue View git blame Copy permalink