Bernard Lang added the comment:
Reply to R.David.Murray
> See also issue 6095.
You are right. I goofed, this is the issue I meant to point to.
> $ ls ''
> ls: cannot access : No such file or directory
> So, the behavior is consistent with the shell.
This is a fair remark.
But still, giving a meaning to something that has none in the shell would not
be an inconsistency either. There are lots of other differences in the Unix
shell design, and strings are often used as a syntactic device. You do not have
to quote file names or paths, unless they raise syntactic problems.
Now if you look at path manipulation commands in the shell, you have :
$ basename aaa
aaa
$ dirname aaa
.
This is a fair choice for the shell since an empty path would print as nothing.
Furthermore, string manipulation is not as convenient with the shell as it is
with Python. So the shell is altogether ignoring the empty path, and string
manipulations (possibly using the empty string) to build a path representation
are not part of the path system.
Python has already made a different choice.
In [4]: os.path.basename('aaa')
Out[4]: 'aaa'
In [5]: os.path.dirname('aaa')
Out[5]: ''
These are the two results of os.path.split('aaa'), which is somewhat the
inverse of os.path.join(...) which I initially considered.
So os.path.dirname in Python does return the empty string '' where the shell
dirname returns a dot. This could also be seen as an inconsistency between Unix
shell and Python.
However, the Unix shell is internally consistent, while taking into account its
own specific constraints.
It seems that it is more important for Python to similarly have its own
internal consistency, especially when considering that Python is already
departing from Unix shell in some minor ways, which are related to the internal
consistency issue that was raised.
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<http://bugs.python.org/issue17545>
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