[Skip Montanaro]
> I reverted the changes to {posix,nt,dos}path.commonprefix this morning,
> updated the tests (still to be checked in) and was starting to work on
> documentation changes, when I realized that something Guido
> said about using dirname to trim to the common directory prefix is
> probably not correct. Here's an example. The common prefix of
> ["/usr/local", "/usr/local/bin"]
> is
> "/usr/local"
> If you blindly apply dirname to that (which is what I think Guido
> suggested as the way to make commonprefix do what I wanted, you wind
> up with
> "/usr"
> which isn't going to be correct on most Unix flavors. Instead, you
> need to check that the prefix doesn't exist or isn't a directory
> before applying dirname.
[Thomas Wouters]
> And even that won't work, in a case like this:
>
> /home/swenson/
> /home/swen/
>
> (common prefix would be /home/swen, which is a directory)
Note that Guido's suggestion does work for that, though.
> or cases like this:
>
> /home/swenson/
> /home/swenniker/
>
> where another directory called
> /home/swen
>
> exists.
Ditto. This isn't coincidence: Guido's suggestion works as-is *provided
that* each dirname in the original collection ends with a path separator.
Change Skip's example to
["/usr/local/", "/usr/local/bin/"]
^ stuck in slashes ^
and Guido's suggestion works fine too. But these are purely
string-crunching functions, and "/usr/local" *screams* "directory" to people
thanks to its specific name. Let's make the test case absurdly "simple":
["/x/y", "/x/y"]
What's the "common (directory) prefix" here? Well, there's simply no way to
know at this level. It's /x/y if y is a directory, or /x if y's just a
regular file. Guido's suggestion returns /x in this case, or /x/y if you
add trailing slashes to both. If you don't tell a string gimmick which
inputs are and aren't directories, you can't expect it to guess.
I'll say again, if you want a new function, press for one! Just leave
commonprefix alone.
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4