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Make _PyDict_Pop() public #111262
Description
Feature or enhancement
Proposal:
It's used, it's reasonable, it's fast, it's already there. Just expose it instead of deleting it.
Has this already been discussed elsewhere?
No response given
Links to previous discussion of this feature:
No response
Activity
serhiy-storchaka commentedon Oct 24, 2023
We should first discuss the design.
The flaws of the current
_PyDict_Pop():Alternative designs of
PyDict_Pop()that do not raise KeyError.PyObject *PyDict_Pop(PyObject *dict, PyObject *key)You have to use
PyErr_Occurred()to distinguish between first two cases.int PyDict_Pop(PyObject *dict, PyObject *key, PyObject **result)*resultto NULL and set exception on error.*resultto NULL and not set exception if the key is not found.*resultto the removed value if the key is found.You have not to use
PyErr_Occurred(). You have to check the returning code or*resultand*resultto the default values after the call if you need it.int PyDict_Pop(PyObject *dict, PyObject *key, PyObject **result)*resultto NULL and set exception on error.*result(which should be initialized with the default value) and not set exception if the key is not found.*resultto the removed value if the key is found.You have to always initialize
*resultbefore the call, but you can simply use*resultafter the call if you treat two last cases the same.These variants do not raise KeyError. If you need KeyError, you have to raise it yourself. Or we can introduce new function which pops item and raises KeyError, or add a flag to raise KeyError. The last two variants have subvariants, how to treat
result == NULL:PyDict_Pop()is used as a variant ofPyDict_DelItem()that tolerates absent keys. It is the most of use cases in the CPython sources.cc @rhettinger, @vstinner
vstinner commentedon Oct 24, 2023
I like to return (-1, 0, 1). But I didn't get details of the API. The definition has not default argument? What is the behavior is default is NULL and the key does not exist.
Is it possible to call it with key=NULL?
scoder commentedon Oct 25, 2023
Ok, I get the pattern. I'll add
_PyDict_Pop()to #111162 so that we have an API until the bike-shedding has settled.pythongh-111262: Re-add _PyDict_Pop() to have a C-API until a new pub…
gh-106320: Re-add some PyLong/PyDict C-API functions (GH-#111162)
vstinner commentedon Oct 27, 2023
That sounds reasonable since 300+ private functions were removed, I don't expect that we can add public replacement quickly enough.
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
pythongh-111262: Add PyDict_Pop() function
gh-111262: Add PyDict_Pop() function (#112028)
vstinner commentedon Nov 14, 2023
After a long discussion, the
int PyDict_Pop(PyObject *p, PyObject *key, PyObject **result)API won: there is no default value anymore. Thanks everyone for this interesting discussion.Thanks @scoder for raising the need for such API.
vstinner commentedon Nov 14, 2023
I wrote python/pythoncapi-compat#81 to add PyDict_Pop() and PyDict_PopString() to pythoncapi-compat: it calls
_PyDict_Pop()on CPython >= 3.5.0b2, or call thedict.pop()method on older Cython versions and on PyPy.pythongh-106320: Re-add some PyLong/PyDict C-API functions (GH-python…
pythongh-111262: Add PyDict_Pop() function (python#112028)
pythongh-106320: Re-add some PyLong/PyDict C-API functions (GH-python…
pythongh-111262: Add PyDict_Pop() function (python#112028)