[Python-Dev] Proposal to revert r54204 (splitext change) (original) (raw)

M.-A. Lemburg mal at egenix.com
Thu Mar 15 08:49:18 CET 2007

On 2007-03-15 07:45, Martin v. Löwis wrote:

Phillip J. Eby schrieb:

And yet, that "incorrect" behavior was clearly intended by the author(s) of the code, test, and docstrings.

As it happens, Guido wrote that code (16 years ago) and the docstring (9 years ago), in the case of the posixpath module at least. I don't find it that clear that it was the intention, AFAICT, it could have been an accident also. Guido added the doc strings as a contribution from Charles G. Waldman; he may just have documented the implemented behavior. In r4493, Sjoerd Mullender changed splitext (in an incompatible way) so that it would split off only the last extension, before, foo.tar.gz would be split into 'foo', '.tar.gz'. So it's clear that the intention was always to "split off the extension", whether or not the behavior on dotfiles was considered I cannot tell. As for Doc/lib, in r6524 Guido changed it to document the actual behavior, from the last component of \var{root} contains no periods, and \var{ext} is empty or begins with a period. to and \var{ext} is empty or begins with a period and contains at most one period. So it seems the original (Guido's) intention was that it splits of all extensions; Sjoerd then changed it to split off only the last extension.

Whatever the intention was or has been: the term "extension" itself is not well-defined, so there's no obvious right way to implement an API that splits off an extension.

E.g. in some cases, .tar.gz is considered an extension, in others, the .gz part is just a transfer encoding and .tar the extension. Then you have .tgz which is a bit of both. It also depends on the platform, e.g. on Windows, only the very last part of a filename is used as extension by the OS to determine the (MIME) type of a file.

As always, it's best to just right your own application-specific code to get defined behavior.

-- Marc-Andre Lemburg eGenix.com

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