id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
32010	Unexpected behaviour of MultiValueDict.getlist in conjunction with map	Etienne Ott	nobody	"When the return value of a call to `MultiValueDict.getlist` is fed into a `map(int, ...)` call, the result has unexpected behaviour when checking the existence of elements with the `in` operator.

Example:
{{{
from django.utils.datastructures import MultiValueDict

mvdict = MultiValueDict({""number"": ""54321""})

mapped = map(int, mvdict.getlist(""number""))
if 1 in mapped:
    print(""1 is found with mvdict"")
else:
    print(""1 isn't found with mvdict"")

mapped = map(int, mvdict.getlist(""number""))
if 54321 in mapped:
    print(""54321 is found with mvdict"")
else:
    print(""54321 isn't found with mvdict"")

single_list = [""54321""]

mapped = map(int, single_list)
if 1 in mapped:
    print(""1 is found with single list"")
else:
    print(""1 isn't found with single list"")

mapped = map(int, single_list)
if 54321 in mapped:
    print(""54321 is found with single list"")
else:
    print(""54321 isn't found with single list"")
}}}

Output:
{{{
1 is found with mvdict
54321 isn't found with mvdict
1 isn't found with single list
54321 is found with single list
}}}

Expected behaviour:
The number 1 is not expected to be found in the list of numbers (which in this example is only one entry), but 54321 is. This assumes that the key of the entry exists in the dict and that the mapping function `int` neither adds nor removes elements due to being able/not able to parse elements as ints. I'm fairly confident both assumptions are met in the example, but the expected behaviour is not.

Remarks:
I admit this use case may seem a bit strange, but it did ""naturally"" come up with a form where a user could select some objects identified by their ID and the form, upon submission, checked for the existence of some IDs in the selected list of IDs in order to do something. My suspicion is that some form of string conversion takes place or that an exception is stringified and taken as a return value. Upon checking if an int exists in the variable, python will then check for the existence of an int in the string. This would explain why the number 1 is found, as it is likely to be found, while the number 54321 isn't."	Bug	closed	Utilities	3.0	Normal	invalid			Unreviewed	0	0	0	0	0	0