Add function to get caller's name: sys._getframemodulename()

[zooba]

BPO	42516
Nosy	@vstinner, @zooba, @corona10, @FFY00

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-11-30.21:54:46.811>
labels = ['interpreter-core', 'type-feature', '3.10']
title = "Add function to get caller's name"
updated_at = <Date 2021-06-11.16:17:34.552>
user = 'https://github.com/zooba'

bugs.python.org fields:

activity = <Date 2021-06-11.16:17:34.552>
actor = 'corona10'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2020-11-30.21:54:46.811>
creator = 'steve.dower'
dependencies = []
files = []
hgrepos = []
issue_num = 42516
keywords = []
message_count = 1.0
messages = ['382199']
nosy_count = 4.0
nosy_names = ['vstinner', 'steve.dower', 'corona10', 'FFY00']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42516'
versions = ['Python 3.10']

Linked PRs

• gh-86682: Adds sys._getframemodulename as a lightweight alternative to _getframe #99520

[zooba]

We have a lot of stdlib code that looks like:

try:
    nm_tpl.__module__ = sys._getframe(2).f_globals.get('__name__', '__main__')
except (AttributeError, ValueError):
    pass

While technically it handles sys._getframe being missing, it would be nice to handle it better for this scenario.

I'm already using a sys._get_calling_module_name() as an internal patch to avoid exposing the _getframe() calls to Python code. (As I recall, it cleans up basically all of the uses apart from the traceback module.) This lets us treat sys._getframe() calls as suspicious, because now most code never uses it.

/*[clinic input]
sys._get_calling_module_name
Return the name of the calling module.
[clinic start generated code]*/
static PyObject *
sys__get_calling_module_name_impl(PyObject *module)
/*[clinic end generated code]*/
{
    PyFrameObject *f = _PyThreadState_GET()->frame;
    PyObject *r;
    if (f == NULL) {
        Py_RETURN_NONE;
    }
    f = f->f_back;
    if (f == NULL) {
        Py_RETURN_NONE;
    }
    r = _PyDict_GetItemIdWithError(f->f_globals, &PyId___name__);
    if (!r) {
        PyErr_Clear();
        r = Py_None;
    }
    Py_INCREF(r);
    return r;
}

For something that will live beyond a separate patch, it might make sense to add as much functionality as needed for the warning module, which currently skips some importlib frames and a caller-specified count. I wouldn't want to make it too much more complex though.

Separating this out would make it easier for other implementations to support enum, typing, collections, and any other modules that want the caller's name, even if they can't easily/efficiently support a full _getframe().

Thoughts?

[JelleZijlstra]

Related: faster-cpython/ideas#238, #90701, #30950.

[zooba]

Hah, I didn't even know about those. Was mostly just trying to cut down on my log spam from everyone calling _getframe all the time :)

[hauntsaninja]

Looks like this was completed