path: root/Lib/re.py

#!/usr/bin/env python
# -*- mode: python -*-

import sys
import string
from pcre import *

#
# First, the public part of the interface:
#

# pcre.error and re.error should be the same, since exceptions can be
# raised from either module.

# compilation flags

I = IGNORECASE
L = LOCALE
M = MULTILINE
S = DOTALL 
X = VERBOSE 

#
#
#

_cache = {}
_MAXCACHE = 20

def _cachecompile(pattern, flags=0):
    key = (pattern, flags)
    try:
	return _cache[key]
    except KeyError:
	pass
    value = compile(pattern, flags)
    if len(_cache) >= _MAXCACHE:
	_cache.clear()
    _cache[key] = value
    return value

def match(pattern, string, flags=0):
    return _cachecompile(pattern, flags).match(string)
  
def search(pattern, string, flags=0):
    return _cachecompile(pattern, flags).search(string)
  
def sub(pattern, repl, string, count=0):
    if type(pattern) == type(''):
	pattern = _cachecompile(pattern)
    return pattern.sub(repl, string, count)

def subn(pattern, repl, string, count=0):
    if type(pattern) == type(''):
	pattern = _cachecompile(pattern)
    return pattern.subn(repl, string, count)
  
def split(pattern, string, maxsplit=0):
    if type(pattern) == type(''):
	pattern = _cachecompile(pattern)
    return pattern.split(string, maxsplit)

def escape(pattern):
    "Escape all non-alphanumeric characters in pattern."
    result = []
    alphanum=string.letters+'_'+string.digits
    for char in pattern:
	if char not in alphanum:
	    result.append('\\')
	result.append(char)
    return string.join(result, '')

def compile(pattern, flags=0):
    "Compile a regular expression pattern, returning a RegexObject."
    groupindex={}
    code=pcre_compile(pattern, flags, groupindex)
    return RegexObject(pattern, flags, code, groupindex)
    

#
#   Class definitions
#

class RegexObject:
    def __init__(self, pattern, flags, code, groupindex):
	self.code = code 
	self.flags = flags
	self.pattern = pattern
	self.groupindex = groupindex

    def search(self, string, pos=0, endpos=None):
	"""Scan through string looking for a match to the pattern, returning
	a MatchObject instance, or None if no match was found."""

	if endpos is None or endpos>len(string): 
	    endpos=len(string)
	if endpos<pos: endpos=pos
	regs = self.code.match(string, pos, endpos, 0)
	if regs is None:
	    return None
	self._num_regs=len(regs)
	
	return MatchObject(self,
			   string,
			   pos, endpos,
			   regs)
    
    def match(self, string, pos=0, endpos=None):
	"""Try to apply the pattern at the start of the string, returning
	a MatchObject instance, or None if no match was found."""

	if endpos is None or endpos>len(string): 
	    endpos=len(string)
	if endpos<pos: endpos=pos
	regs = self.code.match(string, pos, endpos, ANCHORED)
	if regs is None:
	    return None
	self._num_regs=len(regs)
	return MatchObject(self,
			   string,
			   pos, endpos,
			   regs)
    
    def sub(self, 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 self.subn(repl, string, count)[0]
    
    def subn(self, repl, source, 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 string by the
	replacement repl.  number is the number of substitutions that
	were made."""

	if count < 0:
	    raise error, "negative substitution count"
	if count == 0:
	    import sys
	    count = sys.maxint
	if type(repl) == type(''):
	    if '\\' in repl:
		repl = lambda m, r=repl: pcre_expand(m, r)
	    else:
		repl = lambda m, r=repl: r
	n = 0           # Number of matches
	pos = 0         # Where to start searching
	lastmatch = -1  # End of last match
	results = []    # Substrings making up the result
	end = len(source)
	while n < count and pos <= end:
	    m = self.search(source, pos)
	    if not m:
		break
	    i, j = m.span(0)
	    if i == j == lastmatch:
		# Empty match adjacent to previous match
		pos = pos + 1
		results.append(source[lastmatch:pos])
		continue
	    if pos < i:
		results.append(source[pos:i])
	    results.append(repl(m))
	    pos = lastmatch = j
	    if i == j:
		# Last match was empty; don't try here again
		pos = pos + 1
		results.append(source[lastmatch:pos])
	    n = n + 1
	results.append(source[pos:])
	return (string.join(results, ''), n)
									    
    def split(self, source, maxsplit=0):
	"""Split \var{string} by the occurrences of the pattern,
	returning a list containing the resulting substrings."""

	if maxsplit < 0:
	    raise error, "negative split count"
	if maxsplit == 0:
	    import sys
	    maxsplit = sys.maxint
	n = 0
	pos = 0
	lastmatch = 0
	results = []
	end = len(source)
	while n < maxsplit:
	    m = self.search(source, pos)
	    if not m:
		break
	    i, j = m.span(0)
	    if i == j:
		# Empty match
		if pos >= end:
		    break
		pos = pos+1
		continue
	    results.append(source[lastmatch:i])
	    g = m.groups()
	    if g:
		if type(g)==type( "" ): g = [g]
		results[len(results):] = list(g)
	    pos = lastmatch = j
	results.append(source[lastmatch:])
	return results

    # The following 3 functions were contributed by Mike Fletcher, and
    # allow pickling and unpickling of RegexObject instances.
    def __getinitargs__(self):
        return (None,None,None,None) # any 4 elements, to work around
                                     # problems with the
				     # pickle/cPickle modules not yet 
				     # ignoring the __init__ function
    def __getstate__(self):
        return self.pattern, self.flags, self.groupindex
    def __setstate__(self, statetuple):
        self.pattern = statetuple[0]
        self.flags = statetuple[1]
        self.groupindex = statetuple[2]
        self.code = apply(pcre_compile, statetuple)

class MatchObject:
    def __init__(self, re, string, pos, endpos, regs):
	self.re = re
	self.string = string
	self.pos = pos 
	self.endpos = endpos
	self.regs = regs
	
    def start(self, g = 0):
	"Return the start of the substring matched by group g"
	if type(g) == type(''):
	    try:
		g = self.re.groupindex[g]
	    except (KeyError, TypeError):
		raise IndexError, ('group "' + g + '" is undefined')
	return self.regs[g][0]
    
    def end(self, g = 0):
	"Return the end of the substring matched by group g"
	if type(g) == type(''):
	    try:
		g = self.re.groupindex[g]
	    except (KeyError, TypeError):
		raise IndexError, ('group "' + g + '" is undefined')
	return self.regs[g][1]
    
    def span(self, g = 0):
	"""Return a tuple containing the start,end of the substring 
	matched by group g"""
	if type(g) == type(''):
	    try:
		g = self.re.groupindex[g]
	    except (KeyError, TypeError):
		raise IndexError, ('group "' + g + '" is undefined')
	return self.regs[g]
    
    def groups(self):
	"Return a tuple containing all subgroups of the match object"

	# If _num_regs==1, we don't want to call self.group with an
	# empty tuple.
	if self.re._num_regs == 1: return ()
	return apply(self.group, tuple(range(1, self.re._num_regs) ) )

    def group(self, *groups):
	"Return one or more groups of the match."
	if len(groups) == 0:
	    groups = (0,)
	result = []
	for g in groups:
	    if type(g) == type(''):
		try:
		    g = self.re.groupindex[g]
		except (KeyError, TypeError):
		    raise IndexError, ('group "' + g + '" is undefined')
	    if len(self.regs)<=g: raise IndexError, ('group "' + str(g) + '" is undefined')
	    elif (self.regs[g][0] == -1) or (self.regs[g][1] == -1):
		result.append(None)
	    else:
		result.append(self.string[self.regs[g][0]:self.regs[g][1]])
	if len(result) > 1:
	    return tuple(result)
	elif len(result) == 1:
	    return result[0]
	else:
	    return ()