Description

vstinner

opened on Aug 22, 2023

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Feature or enhancement

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Proposal:

Most, if not all, PyDict C APIs have a "String" flavor where the key argument is expressed as a UTF-8 encoded bytes string. But the PyDict_Contains() API is missing such variant.

I suppose that it was not proposed before since PyDict_GetItemString(dict, key) != NULL can already be used. My problem is that PyDict_GetItemString() ignores errors: I would like to report errors.

The newly added PyDict_GetItemStringRef() can be used to check if a dictionary has a key and report errors, but it requires calling Py_DECREF() which is not convenient. Example:

PyObject *value;
if (PyDict_GetItemStringRef(dict, key, &value) < 0) {
    // ... handle error ...
}
int has_value = (value != NULL);
Py_XDECREF(value);
// ... use has_value ...

I would like to be able to replace this code with:

int has_value = PyDict_ContainsString(dict, key);
if (has_value < 0) {    
    // ... handle error ...
}
// ... use has_value ...

There is no need to INCREF/DECREF just to check if a dictionary has a key.

Linked PRs

• gh-108314: Add PyDict_ContainsString() function #108323
• [3.12] gh-108314: PyDict_GetItemString() mentions UTF-8 #108448
• [3.11] [3.12] gh-108314: PyDict_GetItemString() mentions UTF-8 (GH-108448) #108489

Reacted by Kirill Podoprigora and Serhiy Storchaka

Activity

1. vstinner

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Aug 22, 2023
2. Eclips4

   added

   topic-C-API

   on Aug 22, 2023
3. vstinner

   added 3 commits that reference this issue on Aug 22, 2023

   pythongh-108314: Add PyDict_ContainsString() function

   debcd39

   pythongh-108314: Add PyDict_ContainsString() function

   0b41b00

   pythongh-108314: Add PyDict_ContainsString() function

   b142bf9
4. vstinner commented on Aug 22, 2023

   

   vstinner

   on Aug 22, 2023

   MemberAuthor

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   There is already an abstract PyMapping_HasKeyString() function. Sadly, on error, this function clears the exception and returns 0 :-(
5. corona10 commented on Aug 23, 2023

   

   corona10

   on Aug 23, 2023

   Member

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   Has this already been discussed elsewhere?

   FYI, there was the discussion with adding this API.
   capi-workgroup/problems#23
6. encukou commented on Aug 23, 2023

   

   encukou

   on Aug 23, 2023

   Member

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   And here: #100100
7. vstinner

   added 3 commits that reference this issue on Aug 23, 2023

   pythongh-108314: Add PyDict_ContainsString() function

   4916d67

   gh-108314: Add PyDict_ContainsString() function (#108323)

   6726626

   pythongh-108314: PyDict_GetItemString() mentions UTF-8

   2164d65
8. vstinner commented on Aug 24, 2023

   

   vstinner

   on Aug 24, 2023

   MemberAuthor

   More actions

   I added the function to pythoncapi-compat: python/pythoncapi-compat@4734c8e
9. vstinner

   closed this as completedon Aug 24, 2023
10. Yhg1s

    added a commit that references this issue on Aug 25, 2023

    [3.12] gh-108314: PyDict_GetItemString() mentions UTF-8 (#108448)

    9a225d7
11. miss-islington

    added a commit that references this issue on Aug 25, 2023

    [3.12] pythongh-108314: PyDict_GetItemString() mentions UTF-8 (python…

    9609601
12. vstinner

    added a commit that references this issue on Aug 25, 2023

    [3.11] [3.12] gh-108314: PyDict_GetItemString() mentions UTF-8 (GH-10…

    cc81f5b

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