multisub.py

# String substitution by indexing, avoiding recursive replacement.
# 
# Copyright (c) 2009 Rasmus Andersson
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# THE SOFTWARE.

def multisub(src, subs, keytpl=None):
  '''String substitution by indexing, avoiding recursive replacement.
  
  Returns a tuple of ( str result, list indices )
  '''
  # build index
  index = {}
  subsk = {}
  for k,v in subs.items():
    if keytpl:
      k = keytpl % k
    p = 0
    while 1:
      p = src.find(k, p)
      if p == -1:
        break
      index[p] = k
      subsk[k] = v
      p += len(k)
  
  indices = sorted(index.keys())
  dst = src
  
  if indices:
    dst = ''
    srccur = 0
    for p in indices:
      k = index[p]
      dst += src[srccur:p]
      dst += subsk[k]
      srccur = p+len(k)
    dst += src[srccur:]
  
  return dst, indices