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cpython/Lib/sre.py

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#
# 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.
#
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:]
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