os.mkdir(path) returns OSError when directory does not exist

I am calling os.mkdir to create a folder with a certain set of generated data. However, even though the path I specified has not been created, the os.mkdir(path) raises an OSError that the path already exists.

For example, I call:

os.mkdir(test)

This call results in OSError: [Errno 17] File exists: 'test' even though I don't have a test directory or a file named test anywhere.

NOTE: the actual path name I use is not "test" but something more obscure that I'm sure is not named anywhere.

Help, please?

Solution 1:

Greg's answer is correct but doesn't go far enough. OSError has sub-error conditions, and you don't want to suppress them all every time. It's prudent to trap just expected OS errors.

Do additional checking before you decide to suppress the exception, like this:

import errno
import os

try:
    os.mkdir(dirname)
except OSError as exc:
    if exc.errno != errno.EEXIST:
        raise
    pass

You probably don't want to suppress errno.EACCES (Permission denied), errno.ENOSPC (No space left on device), errno.EROFS (Read-only file system) etc. Or maybe you do want to -- but that needs to be a conscious decision based on the specific logic of what you're building.

Greg's code suppresses all OS errors; that's unsafe just like except Exception is unsafe.

As others have pointed out, newer versions of Python provide os.makedirs() that attempts to create the dir only if it doesn't exist, equivalent to mkdir -p from a unix command line.

Solution 2:

In Python 3.2 and above, you can use:

os.makedirs(path, exist_ok=True)

to avoid getting an exception if the directory already exists. This will still raise an exception if path exists and is not a directory.