[Python-Dev] A wart which should have been repaired in 3.0?

Nick Coghlan ncoghlan at gmail.com
Sat Dec 27 00:58:07 CET 2008

skip at pobox.com wrote:
> The doc for os.path.commonprefix states:
>     Return the longest path prefix (taken character-by-character) that is a
>     prefix of all paths in list. If list is empty, return the empty string
>     (''). Note that this may return invalid paths because it works a
>     character at a time.
> I remember encountering this in an earlier version of Python 2.x (maybe 2.2
> or 2.3?) and "fixed" it to work by pathname components instead of by
> characters.  That had to be reverted because it was a behavior change and
> broke code which used it for strings which didn't represent paths.  After
> the reversion I then forgot about it.
> I just stumbled upon it again.  It seems to me this would have been a good
> thing to fix in 3.0.  Is this something which could change in 3.1 (or be
> deprecated in 3.1 with deletion in 3.2)?

Why can't we add an "allow_fragment" keyword that defaults to True? Then
"allow_fragment=False" will stop at the last full directory name and
ignore any partial matches on the filenames or the next subdirectory
(depending on where the common prefix ends).


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

More information about the Python-Dev mailing list