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itertools: defer dropwhile predicate validation #8504

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Merged
youknowone merged 1 commit into from
Aug 12, 2026
+4 −6
Merged

itertools: defer dropwhile predicate validation #8504

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1 change: 0 additions & 1 deletion Lib/test/test_itertools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1260,7 +1260,6 @@ def test_takewhile(self):
self.assertEqual(list(t), [1, 1, 1])
self.assertRaises(StopIteration, next, t)

@unittest.expectedFailure # TODO: RUSTPYTHON
def test_dropwhile(self):
data = [1, 3, 5, 20, 2, 4, 6, 8]
self.assertEqual(list(dropwhile(underten, data)), [20, 2, 4, 6, 8])
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9 changes: 4 additions & 5 deletions crates/vm/src/stdlib/itertools.rs
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Expand Up @@ -10,7 +10,7 @@ mod decl {
rc::PyRc,
},
convert::ToPyObject,
function::{ArgCallable, FuncArgs, OptionalArg, OptionalOption, PosArgs},
function::{FuncArgs, OptionalArg, OptionalOption, PosArgs},
protocol::{PyIter, PyIterReturn, PyNumber},
raise_if_stop,
stdlib::sys,
Expand Down Expand Up @@ -477,15 +477,15 @@ mod decl {
#[pyclass(name = "dropwhile")]
#[derive(Debug, PyPayload)]
struct PyItertoolsDropwhile {
predicate: ArgCallable,
predicate: PyObjectRef,
iterable: PyIter,
start_flag: AtomicCell<bool>,
}

#[derive(FromArgs)]
struct DropwhileNewArgs {
#[pyarg(positional)]
predicate: ArgCallable,
predicate: PyObjectRef,
#[pyarg(positional)]
iterable: PyIter,
}
Expand Down Expand Up @@ -522,8 +522,7 @@ mod decl {
if !zelf.start_flag.load() {
loop {
let obj = raise_if_stop!(iterable.next(vm)?);
let pred = predicate.clone();
let pred_value = pred.invoke((obj.clone(),), vm)?;
let pred_value = predicate.call((obj.clone(),), vm)?;
if !pred_value.try_to_bool(vm)? {
zelf.start_flag.store(true);
return Ok(PyIterReturn::Return(obj));
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