Open file on separate drive in python

Question

I have an annoying problem in python 2.7 on windows XP. I've got some code that collects a file name off the command line with the argparse library. I then try and open said file. Normally, this works fine, and if you pass in a full path name it successfully opens that too. However, if the path uses a drive letter other than the location you started from, python fails with an IO error, stating that the file or directory does not exist.

For example:

C:\>schema_split.py "C:\path\to\file"
works!
C:\>schema_split.py "I:\path\to\file"
fails!

Relevant code section:

parser = argparse.ArgumentParser(description='Process the Accounting file.', version='%(prog)s 1.1')
parser.add_argument('infile', nargs="+", type=str, help='list of input files')
# get the current arguments and put them into a variable
args = parser.parse_args()
for f in args.infile:
    with open(f, "rb") as mycsv:

I don't know why python would have problems with alternate drive letters. The only thing I can come up with is that we run it on a shared drive mapped to a local drive. But for all intents and purposes, the program shouldn't "see" the fact that it is operating on a remote drive.

Thoughts?

Answer 1

I think you may want to try two slashes instead of 1. Also I think this SO Question might be helpful to you.

Two slashes like this C:\>schema_split.py "I:\\path\to\file"

Hope this is helpful.

Answer 2

You are assuming python is having problems with drive letters. It isn't. Your problem is something else.

C:\>python
Python 2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> f = open(r"U:\foo.txt")
>>> 

As you can see opened a file from another drive using backslashes without error.

Use the following script to diagnose your problem:

import os
import sys

path = sys.argv[1]
basepath, fname = os.path.split(path)
print "directory:", basepath
if os.path.exists(basepath):
    print "directory exists"
else:
    print "directory does not exist!"
    sys.exit()

if not fname:
    print "no filename provided!"
    sys.exit()
print "filename:", fname
if os.path.exists(path):
    print "filename exists"
else:
    print "filename not found!"
    print "directory contents:"
    for fn in os.listdir(basepath):
        print fn

Pass your path to the script and it will test the path and file name you pass to it.