[C API] Add PySys_GetAttr() function

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Feature or enhancement

Proposal:

The existing PySys_GetObject() function has two issues:

• It returns a borrowed reference.
• It ignores errors.

I propose adding new functions PySys_GetAttr() and PySys_GetAttrString() to get a sys module attribute which return a strong reference and don't ignore errors.

API:

PyObject *PySys_GetAttr(PyObject *name)
PyObject *PySys_GetAttrString(const char *name)

• Return a new object (strong reference) on success.

• Set an exception and return NULL on error:

  • Set an AttributeError if the attribute doesn't exist.
  • Set a RuntimeError if the sys module cannot be retrieved.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-129367: Add PySys_GetAttr() function #129369

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An alternative would be to accept an object and add a String function for the const char* argument:

PyObject *PySys_GetAttr(PyObject *name)
PyObject *PySys_GetAttrString(const char *name)

I'm not sure if it's worth it to have an alternative with PyObject*.

UPDATE: I added PySys_GetAttrString(). @serhiy-storchaka conducted a code analysis in 2023 and found that we need a function which takes a PyObject* name.

By the way, I'm also proposing to add PyImport_ImportModuleAttrString(mod_name, attr_name) which is similar: PyImport_ImportModuleAttrString("sys", "path") can be used to get sys.path for example. See issue #128911.

IMO it's still relevant to add PySys_GetAttrString(name) even if PyImport_ImportModuleAttrString(mod_name, attr_name) is added: PySys_GetAttrString(name) is faster, it doesn't have to go into the importlib machinery.

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See also #108512 "C API: Add a replacement for PySys_GetObject".

[serhiy-storchaka]

Isn't it a duplicate of #108512? That issue turned out to be more complex, because we have at least 4 different functions that implements this with different particularities.

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Isn't it a duplicate of #108512?

Right. I close my issue.