#35915: QueryDict __getitem__ returns an empty list when the value is an empty
list
-------------------------------------+-------------------------------------
Reporter: Nguyễn Hồng Quân | Owner:
Type: | jburns6789
Cleanup/optimization | Status: assigned
Component: HTTP handling | Version: 5.1
Severity: Normal | Resolution:
Keywords: querydict | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by David Sanders:
Old description:
> Though [https://docs.djangoproject.com/en/5.1/ref/request-
> response/#django.http.QueryDict.__getitem__ documentation] says that
>
> QueryDict.!__getitem!__(key)
> Returns the value for the given key. If the key has more than one
> value, it returns the last value.
>
> It returns a list when the raw value is an empty list:
>
> {{{#!python
> >>> from django.http import QueryDict
> >>> q = QueryDict('a=1', mutable=True)
> >>> q['a']
> '1'
>
> >>> q.setlist('b', [])
> >>> q['b']
> []
> }}}
>
> which surprises user and it even not mentioned in documentation.
>
> Could we change this behavior? I know that we don't have a perfect
> solution, but returning `None` in this case is less bad than empty list
> `[]`, because it is easier to annotate type.
>
> - If returns `None`, we can annotate type as `str | None`.
> - If returns `[]`, Python doesn't have an exact type for empty list, and
> `django-stubs` has to annotate as `str | list[object]` which is quite
> broader than the actual value (empty list).
New description:
**Update:** forum post: https://forum.djangoproject.com/t/change-
querydict-getitem-in-case-of-empty-list/36522
Though [https://docs.djangoproject.com/en/5.1/ref/request-
response/#django.http.QueryDict.__getitem__ documentation] says that
QueryDict.!__getitem!__(key)
Returns the value for the given key. If the key has more than one
value, it returns the last value.
It returns a list when the raw value is an empty list:
{{{#!python
>>> from django.http import QueryDict
>>> q = QueryDict('a=1', mutable=True)
>>> q['a']
'1'
>>> q.setlist('b', [])
>>> q['b']
[]
}}}
which surprises user and it even not mentioned in documentation.
Could we change this behavior? I know that we don't have a perfect
solution, but returning `None` in this case is less bad than empty list
`[]`, because it is easier to annotate type.
- If returns `None`, we can annotate type as `str | None`.
- If returns `[]`, Python doesn't have an exact type for empty list, and
`django-stubs` has to annotate as `str | list[object]` which is quite
broader than the actual value (empty list).
--
--
Ticket URL: <https://code.djangoproject.com/ticket/35915#comment:10>
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