python os.path.exists reports False when files is there

Question

Hi have an application which is sometimes reporting that a file does not exist even when it does, I am using os.path.exists and the file is on a mounted network share. I am on OSX Yosemite, python 2.7.9 and I have access rights to the file. Here's the weird thing. The first command below reports False, I then run it again but change one of the characters in the file name to lowercase (TestVendorid_VerifyLog.txt), run it again and it reports True! Then run it again with the upper case again (TestVendorId_VerifyLog.txt) and it reports True! What is going on? This is quite consistent, in that it returns True most of the time, but then all of a sudden return False, then I can repeat the below exercise.

>>> import os
>>> os.path.exists("/Volumes/platform-deliveries-103_1/TEST/TestVendorId.itmsp/TestVendorId_VerifyLog.txt")
False
>>> os.path.exists("/Volumes/platform-deliveries-103_1/TEST/TestVendorId.itmsp/TestVendorid_VerifyLog.txt")
True
>>> os.path.exists("/Volumes/platform-deliveries-103_1/TEST/TestVendorId.itmsp/TestVendorId_VerifyLog.txt")
True
>>>

UPDATE 1:

When it is reporting True, I ran this:

>>> os.stat("/Volumes/platform-deliveries-103_1/TEST/TestVendorId.itmsp/TestVendorId_VerifyLog.txt")
posix.stat_result(st_mode=33216, st_ino=5351561660274954203, st_dev=771751953L, st_nlink=1, st_uid=504, st_gid=20, st_size=38552, st_atime=1428492003, st_mtime=1428589374, st_ctime=1428589374)

UPDATE 2:

OK, I can now repeat this and it is definitely a cache thing. I delete the file TestVendorId_VerifyLog.txt on my local Mac, then recreate the file on another workstation (this file is on a network share) I then get False on my Mac. If I change a letter in the file name of the os.path.exists command, it seems to make os.path.exists take a harder look for the file and finds it. So what I need is a 'Refresh Finder' command in python just prior to running the command.

Are you running on a file system that is case sensitive? A different case is a different file. Linux is case sensitive. — Robert Jacobs, Apr 09 '15 at 14:52
Which file is really on your filesystem? Is it case sensitive? I agree its a problem in either case, but we still want to know to help understand the problem. — Robert Jacobs, Apr 09 '15 at 15:00
Maybe the problem isn't fixed by changing the case, but in running the command twice? Try running the exact function twice (don't change case) to see. — Robert Jacobs, Apr 09 '15 at 15:06
Ran it 5 times in a row, False every-time, change a case of one of the letters and bingo, True. It is definitely a cache thing on Mac. I will update the question with my findings. — speedyrazor, Apr 09 '15 at 15:13
Same problem, we should maybe try again for X times: https://stackoverflow.com/a/2083996/1486850 — JinSnow, Dec 11 '18 at 13:29

score 3 · Answer 1 · answered Apr 09 '15 at 14:54

3

os.path.exists returns False when an OSError is happening while it tries to stat the file. The exception is handled and therefor masked.

You should try to run os.stat(filename) to see if that gives further information on the problem.

answered Apr 09 '15 at 14:54

Klaus D.

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So helpful - thank you. Really annoying that the error does not show up when using `os.path.exists()` – HFBrowning Mar 27 '23 at 21:54

joarleymoraes · Answer 2 · 2017-05-11T20:19:57.887

0

Make sure there is not a \n or any other 'invisible' character anywhere in your filename.

Edit: After a few hours digging on a similar problem of my own, I realized the problem was wrong permission for the directory where my target file was in. Make sure you ls -l on your directory to check whether the user you are using has the proper permission.

edited May 11 '17 at 20:19

answered May 11 '17 at 19:16

joarleymoraes

1,891
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python os.path.exists reports False when files is there

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