[Python-Dev] Best Python API for exposing posix_spawn

[Pablo Galindo Salgado]

Hi,

I'm currently working on exposing posix_spawn in the posix module (and by
extension in the os module). You can find the initial implementation in
this PR:

https://github.com/python/cpython/pull/5109

As pointed out by Gregory P. Smith, some changes are needed in the way the
file_actions arguments is passed from Python. For context, posix_spawn has
the following declaration:

int posix_spawn(pid_t *pid, const char *path,
const posix_spawn_file_actions_t *file_actions,
const posix_spawnattr_t *attrp,
char *const argv[], char *const envp[]);

Here, file_actions is an object that represents a list of file actions
(open, close or dup2) that is populated using helper functions on the C API.

The question is: what is the best way to deal with this argument?

Following Gregory's comment on the PR I understand that he is proposing to
have three objects in the os module representing each action and pass a
sequence of these objects to the Python API. What I am not sure about this
is that there is no previous example of such classes in the os module for
other similar APIs and therefore I am not sure if there is a better
approach.

Thanks you very much for your time!

Pablo Galindo
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