I just ran across errno 39 (Directory not empty) when using Path.rename(newdir) when newdir already existed and was not empty.  I realized that OSError exceptions don't have a DirectoryNotEmptyError subclass.  Maybe we should add one?

Probably not important or common enough to add for 3.7 given we're in beta now.

> Maybe we should add one?

I don't think that we need to add an *builtin* exception for every single possible errno. On Linux with Python 3.7, I count 133 different error numbers:

>>> len([name for name in dir(errno) if name.startswith("E")])
133

PEP 3151 explains the rationale for added OSError subclasses.

I think that we should focus on the most common ones, especially the ones which are available on all platforms.

I have no opinion about "errno 39 (Directory not empty)". Is it a "common" error?

> I have no opinion about "errno 39 (Directory not empty)". 
> Is it a "common" error?

Python's code base never specifically handles ENOTEMPTY. On the other hand, in terms of basic operations on files and directories, I think implementing DirectoryNotEmptyError follows naturally from the existing set: FileNotFoundError, FileExistsError, NotADirectoryError, and IsADirectoryError.

According to POSIX, the only system calls that can fail with ENOTEMPTY are rmdir(), rename() and unlinkat().

Copy of my comment on the review:
https://github.com/python/cpython/pull/15496#pullrequestreview-287311626

I'm not excited by adding a new builtin symbol: IMHO this module already exists too many symbols.

I'm not convinced that it's worth it. There is exactly 0 line of code in CPython code base which expects ENOTEMPTY errno. So it looks like an artifical use case.

I recall that when PEP 3151 was implemented, the implementation replaced a lot of code using "except OSError as exc: if exc.errno == XXX: ... else: raise" with "except : ..." which was neat.

But again, I don't see any usage of ENOTEMPTY in the Python stdlib.

Are you aware of 3rd party code expecting ENOTEMPTY? How many projects?

Adding a builtin symbol is a significant change, it should be well motived.

> Python's code base never specifically handles ENOTEMPTY.

Right, so this use case looks artificial to me.


> On the other hand, in terms of basic operations on files and directories, I think implementing DirectoryNotEmptyError follows naturally from the existing set: FileNotFoundError, FileExistsError, NotADirectoryError, and IsADirectoryError.

Again, I consider that we must not add one exception per errno, since the Python errno module contains 133 error codes on Linux. Many are very rare and don't deserve to add a new symbol to the builtins module.

I suggest to close this issue.

If later someone wants to get DirectoryNotEmptyError, please open a new issue with statistics of how many 3rd party projects use ENOTEMPTY.

versions: + Python 3.9, - Python 3.8