Os.path : can you explain this behavior?

Question

I love Python because it comes batteries included, and I use built-in functions, a lot, to do the dirty job for me.

I have always been using happily the os.path module to deal with file path but recently I ended up with unexpected results on Python 2.5 under Ubuntu linux, while dealing with string that represent windows file paths :

filepath = r"c:\ttemp\FILEPA~1.EXE"
print os.path.basename(filepath)
'c:\\ttemp\\FILEPA~1.EXE']
print os.path.splitdrive(filepath)
('', 'c:\ttemp\\FILEPA~1.EXE')

WTF ?

It ends up the same way with filepath = u"c:\ttemp\FILEPA~1.EXE" and filepath = "c:\ttemp\FILEPA~1.EXE".

Do you have a clue ? Ubuntu use UTF8 but I don't feel like it has something to do with it. Maybe my Python install is messed up but I did not perform any particular tweak on it that I can remember.

You might want to review your accepted answer -- see Moe's reference to ntpath, which is the Right Way to do this. — Charles Duffy, Oct 08 '08 at 19:55

score 26 · Accepted Answer · answered Oct 08 '08 at 12:11

26

If you want to manipulate Windows paths on linux you should use the ntpath module (this is the module that is imported as os.path on windows - posixpath is imported as os.path on linux)

>>> import ntpath
>>> filepath = r"c:\ttemp\FILEPA~1.EXE"
>>> print ntpath.basename(filepath)
FILEPA~1.EXE
>>> print ntpath.splitdrive(filepath)
('c:', '\\ttemp\\FILEPA~1.EXE')

answered Oct 08 '08 at 12:11

Moe

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This is an excellent answer that deserves to be the accepted one, IMHO. It is much better to use ready-made tools than craft your own regexps. – Eli Bendersky Oct 08 '08 at 13:29

kender · Answer 2 · 2008-10-08T11:50:24.820

4

From a os.path documentation:

os.path.splitdrive(path)
Split the pathname path into a pair (drive, tail) where drive is either a drive specification or the empty string. On systems which do not use drive specifications, drive will always be the empty string. In all cases, drive + tail will be the same as path.

If you running this on unix, it doesnt use drive specifications, hence - drive will be empty string.

If you want to solve windows paths on any platform, you can just use a simple regexp:

import re
(drive, tail) = re.compile('([a-zA-Z]\:){0,1}(.*)').match(filepath).groups()

drive will be a drive letter followed by : (eg. c:, u:) or None, and tail the whole rest :)

edited Oct 08 '08 at 11:50

answered Oct 08 '08 at 11:38

kender

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Yep, just realize that : the string process is based on the OS, not on syntax. It does not make any difference between win and unix path, it just apply a different algo according to you platform. Crap. – Bite code Oct 08 '08 at 11:40
Don't use regular expressions, use the ntpath module instead - see my answer. – Moe Oct 08 '08 at 12:13
I agree :) Never had to deal with windows-style patchs, just had no idea of that module:) – kender Oct 09 '08 at 04:48

score 1 · Answer 3 · answered Oct 08 '08 at 11:39

1

See the documentation here, specifically:

splitdrive(p) Split a pathname into drive and path. On Posix, drive is always empty.

So this won't work on a Linux box.

answered Oct 08 '08 at 11:39

Adam Bellaire

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Os.path : can you explain this behavior?

3 Answers3

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