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Match CPython's str subscript TypeError message #8319

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Match CPython's str subscript TypeError message #8319

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6ecda1b
Match CPython's str subscript TypeError message
kim-jaedeok Jul 16, 2026
52d0bb3
Fold str's subscript TypeError into the shared index helper
kim-jaedeok Jul 28, 2026
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1 change: 0 additions & 1 deletion Lib/test/string_tests.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1301,7 +1301,6 @@ def test___contains__(self):
self.checkequal(False, 'asd', '__contains__', 'asdf')
self.checkequal(False, '', '__contains__', 'asdf')

@unittest.expectedFailure # TODO: RUSTPYTHON
def test_subscript(self):
self.checkequal('a', 'abc', '__getitem__', 0)
self.checkequal('c', 'abc', '__getitem__', -1)
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6 changes: 6 additions & 0 deletions crates/vm/src/sliceable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -275,6 +275,12 @@ impl SequenceIndex {
i?.try_to_primitive(vm)
.map_err(|_| vm.new_index_error("cannot fit 'int' into an index-sized integer"))
.map(Self::Int)
} else if type_name == "str" {
// CPython's unicode_subscript raises a distinct message here.
Err(vm.new_type_error(format!(
"string indices must be integers, not '{}'",

@moreal moreal Aug 9, 2026

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It is trivial but there is a limit for the class name

https://github.com/python/cpython/blob/823f0323ee6ec1402088b73bce1a38473cac36dc/Objects/unicodeobject.c#L14645-L14648

obj.class()
)))
} else {
Err(vm.new_type_error(format!(
"{} indices must be integers or slices or classes that override __index__ operator, not '{}'",
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