Strange os.path.exists( ) behaviour

[Pierre Quentel]

os.path.exists( path) returns True if "path" exists

But on Windows it also returns True for "path" followed by any number of
dots :

Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright" , "credits" or "license" for more information.

import os
os.path.exists( 'Lib/os.py') True # expected os.path.exists( 'Lib/os.py.') True # unexpected os.path.exists( 'Lib/os.py.....') True # unexpected

Is there a reason for this ? Is there a test that returns True only for
the really existing path ?

Pierre

[Jeff Epler]

Pierre wrote:

Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit (Intel)] on win32

^^^^^^^
Here's the bug. You're using Windows. It's a filesystem, but not as we know it...

Anyway, You are getting exactly what the low-level Windows APIs return.

Here's a small "C" program. It prints "0" next to the filename if the
file exists, -1 otherwise, as described at
http://msdn.microsoft.com/library/de..._._waccess.asp

int main(int argc, char **argv) {
int i;
for(i=1; i<argc; i++) {
printf("%20s: %d\n", argv[i], _access(argv[i], 0));
}
}

I compiled it with "i386-mingw32msvc-gcc -o a.exe exist.c"

Here's an example session with it:
C:\TMP\example> dir
Volume in drive C has no label.
Volume Serial Number is 171D-4D2A

Directory of C:\TMP\example

07/06/05 03:04p <DIR> .
07/06/05 03:04p <DIR> ..
07/06/05 03:05p 3 exist
3 File(s) 3 bytes

C:\TMP\example> x:a.exe exist exist. exist.... nonexist nonexist. nonexist...
exist: 0
exist.: 0
exist....: 0
nonexist: -1
nonexist.: -1
nonexist...: -1

C:\TMP\example> type nonexist....
The system cannot find the file specified.

C:\TMP\example> type exist....
C:\TMP\example>

As you can see, not only does Windows think that "exist...." exists, but itcan
successfully "type" its contents too!

Jeff

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[Michael Hoffman]

Jeff Epler wrote:

Here's the bug. You're using Windows.

QOTW (speaking as someone who is using Windows right now).
--
Michael Hoffman

[Sion Arrowsmith]

Jeff Epler <je****@unpytho nic.net> wrote:

Pierre wrote:

Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit (Intel)] on wi=

n32
^^^^=
^^^
Here's the bug. You're using Windows. It's a filesystem, but not as we kn=
ow it...
[ ... ]
As you can see, not only does Windows think that "exist...." exists, but it=
can
successfully "type" its contents too!

The "reason" for this behaviour is that the concept of a file
extension is firmly embedded in the operating system. exists is a
file with no extension, as is exists. (no, it doesn't make a
distinction between "no extension" and "an empty extension").
From there it's not too great a leap of induction to suppose that
exists.... is the same file called exists with no extension. It's
not unlike being able to stick an arbitrary number of /s onto the
end of a directory name on a sane OS/filesystem.

--
\S -- si***@chiark.gr eenend.org.uk -- http://www.chaos.org.uk/~sion/
___ | "Frankly I have no feelings towards penguins one way or the other"
\X/ | -- Arthur C. Clarke
her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump

[Casey Hawthorne]

Does this work differently under other platforms?

Pierre Quentel <qu************ @wanadoo.fr> wrote:

os.path.exists (path) returns True if "path" exists

But on Windows it also returns True for "path" followed by any number of
dots :

Python 2.4 (#60, Nov 30 2004, 11:49:19) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright" , "credits" or "license" for more information.

import os
os.path.exists( 'Lib/os.py')True # expected os.path.exists( 'Lib/os.py.')True # unexpected os.path.exists( 'Lib/os.py.....')True # unexpected

Is there a reason for this ? Is there a test that returns True only for
the really existing path ?

Pierre

--
Regards,
Casey