bpo-14208 was ultimately resolved through an import system specific solution, with PEP-451 making the module name passed to python -m available as __main__.__spec__.name.

However, there are other situations where it may be useful to offer an implementation-dependent attribute in the sys module that provides access to a copy of the host application's raw argv details, rather than the filtered sys.argv details that are left after the host application's command line processing has been completed.

In the case of CPython, where sys.argv represents the arguments to the Python level main function, sys._raw_argv would be a copy of the argv argument to the C level main() or wmain() function (as appropriate for the platform).

As bytes?

For CPython, I was thinking of having it be "whatever gets passed to Py_Main", and that accepts wchar_t in Py3 [1], so on *Nix systems, the command line has already been decoded with [2] by the time it runs.

[1] https://docs.python.org/3/c-api/veryhigh.html#c.Py_Main
[2] https://docs.python.org/3/c-api/sys.html#c.Py_DecodeLocale

In the case of Windows, the wchar_t array is received straight from the OS as UTF-16-LE.

Why is the name flagged as a private implementation detail? I.e. a single leading underscore. I'd be reluctant to rely on this in production code, given how strong the _private convention is.

Suggest just sys.raw_args instead.

As bytes?

No, text please. Text is just more convenient in Python, and it's trivial to retrieve original bytes:

raw_args_bytes = [os.fsencode(arg) for arg in sys._raw_args]

On Mar 21, 2017, at 11:47 AM, STINNER Victor wrote:

No, text please. Text is just more convenient in Python, and it's trivial to
retrieve original bytes:

raw_args_bytes = [os.fsencode(arg) for arg in sys._raw_args]

Well, "raw args" implies minimal or no processing, so bytes would make the
most sense. It doesn't bother me that it's inconvenient; this won't be an oft
used API and the conversion to strings should be just as easy.

Well, "raw args" implies minimal or no processing,

Ok, so call it "original", sys.orig_arv, in that case ;-)

There is already an existing public C API get retrieve original program arguments *as text*:

/* Make the *original* argc/argv available to other modules.
This is rare, but it is needed by the secureware extension. */

void
Py_GetArgcArgv(int *argc, wchar_t ***argv)
{
    *argc = orig_argc;
    *argv = orig_argv;
}

Are you talking about exposing these arguments at the Python level?

@steven This is an implementation detail in the same sense that sys._getframe() is: it's not something that's actually going to make sense in all contexts. For example, if Py_Main() is never called (for CPython), it would still be None, and other implementations may not define it at all. And even when it's set for CPython, the exact details of what it contains are going to be at least somewhat platform dependent.

@barry On Windows we define mainw rather than main, so it's the UTF-16-LE encoded text that is the "raw" form. That means the "raw" here refers to "before the Python interpreter CLI processing" - the normalization step to get the command line to wchar_t regardless of platform isn't going to be skipped (since the interpreter runtime itself never even sees the raw bytes in Python 3).

One option would be to use a longer name like sys._executable_argv, since in the typical case, sys.executable and sys._executable_argv[0] will be the same.

@victor It wouldn't be exactly the same as Py_GetArgcArgv, as I'd propose making a pristine copy *before* Py_Main() mutates anything - we do some in-place editing of entries while figuring out what "sys.argv[0]" should look like at the Python level.

For example, if Py_Main() is never called (for CPython), it would still be None,

What is the content of sys.argv in that case? Can't we use the same value for sys._raw_argv?

If the embedding application doesn't call PySys_SetArgv or PySys_SetArgvEx, then there is no argv attribute defined in the sys module (I wasn't actually sure what happened in that case, so I went and checked the code).

For the reference CLI, the relevant call happens in Py_Main() after all the interpreter level arguments have been processed.

If the embedding application doesn't call PySys_SetArgv or PySys_SetArgvEx, then there is no argv attribute defined in the sys module (I wasn't actually sure what happened in that case, so I went and checked the code).

Ok, so just don't define sys._raw_argv in that case. But it doesn't seem enough to me to justify to make the attribute private.

https://docs.python.org/dev/library/sys.html#sys.getallocatedblocks can be seen as an implementation detail.The method name has no underscore prefix, but a simple fallback: return 0 if the feature is is not implemented.

OK, I've changed the proposed attribute name to be sys.executable_argv, with the rationale being that it's "argv as originally seen by sys.executable, rather than by Python's main module"

As part of documenting this, both it and the argv documentation can make it clear that they may be entirely absent if the host application doesn't set them.

I mark this issue as a duplicate of bpo-23427 which has patch and is older.