Following code:

```
from pathlib import Path
import os
import subprocess

dir_name = os.environ.get("WORKSPACE", None) or "."
output_directory = Path(dir_name) / "results"
res = subprocess.run(["mytest", "--output", output_directory])
```

Works on macos and linux but on windows, this causes "TypeError: argument of type 'WindowsPath' is not iterable" at https://github.com/python/cpython/blob/master/Lib/subprocess.py#L568

(line is different, depending on the actual python release but i guess that gives the idea where it is)..

Quick test to check if i can do  `" " in Path("/tmp")` on posix platforms shows the same exception but with PosixPath type but apparently this sort of check does not happen on those platforms as the example code works fine there.

It would be nice to be able to pass path objects to subprocess api calls also in windows without explicitly casting the object into string before passing it as argument.

See also https://bugs.python.org/issue31961

@xtreak

I went thru the comments of the report you linked. It definitely looks like the discussion was related  but it didnt really fix the issue here.

https://bugs.python.org/issue31961#msg311775 without trying out, that comment actually touches the underlying issue, on windows, list2cmdline throws that typeerror because iterated argument list (output_directory in my example) is WindowsPath and thus not iterable and and testing the arg with "in" operator fails ..

I do not understand how you get this result. At that line of code arg can only be string, because it is a result of os.fsdecode(). Are you sure that you use Python version which includes issue31961 changes? What exactly Python version do you use?

I closed #41753 as a duplicate of this.  

On that issue, Eryk Sun said "The underlying subprocess.Popen class was updated in 3.8 to support path-like objects in `args` (with shell=False) and `executable` on Windows [1]. This change was not backported to 3.6 and 3.7."

The latter is because 3.6 and 3.7 only get security patches.  Jani, please verify that this is still an issue with 3.8 and/or 3.9.