suggestion for os.path.commonprefix

[Cristian Barbarosie]

One line dissapeared misteriously from the code in my previous posting.
(if number_of_paths == 0) Below is the full version. Sorry for the typo.

One more comment: yes, I suppose dirname could be defined as
def dirname(path): return commonprefix([path])

Cristian Barbarosie
http://www.lmc.fc.ul.pt/~barbaros
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def commonprefix (list_of_paths):
  """Like in os.path, but more in the spirit of path manipulation.
  Items must end in os.sep if they represent directories."""
  number_of_paths = len(list_of_paths)
  if number_of_paths == 0: return ''
  first_path = list_of_paths[0]
  largest_i = -1
  for i in range(len(first_path)):
    stop = 0
    character = first_path[i]
    for n in range(1,number_of_paths):
      item = list_of_paths[n]
      if (i >= len(item)) or (character <> item[i]):
        # here we took advantage of the way Python evaluates
        # logical expressions: if the first one is true,
        # then the second one is not evaluated
        stop = 1
        break
    if stop: break
    if character == os.sep: largest_i = i
  prefix = first_path[:largest_i+1]
  return prefix