bpo-8232 has a patch to add an `arguments` parameter to os.startfile(). This improvement is needlessly tied to that issue. It's useful in general as a safer way to execute applications and scripts compared to using subprocess.Popen() with shell=True. It also enables passing arguments to applications and scripts when using the "runas" operation (prompts with a UAC dialog) and "runasuser" operation (prompts with a credential dialog). The latter operations are supported by default for binary executables and batch scripts in Windows 10, and they can be implemented by the progid of any file type.

Setting the working directory with a cwd parameter is not as generally useful, but it's not entirely useless and simple to add at the same time when adding the `args` parameter.

Not rushing this one in, but this is a relatively straightforward addition that will definitely be handy in some situations.

I didn't bother adding an enum for the SW_* constants, since I don't think they'll get anywhere near enough use to justify being in our public API. Kind of like error codes, which we already don't expose everywhere even though we use them ourselves as raw numbers.

New changeset 019e9e816882f5c43c4b833f81844b8299e815fd by Steve Dower in branch 'master':
bpo-43538: Add extra arguments to os.startfile (GH-25538)
https://github.com/python/cpython/commit/019e9e816882f5c43c4b833f81844b8299e815fd