Merge pull request #1294 from corona10/itertools_filterfalse

itertools: Implement itertools.filterfalse

tests/snippets/stdlib_itertools.py

@@ -183,3 +183,21 @@ assert_matches_seq(it, [1, 2])
 
 it = i([1, 2, 3], None, None, 3)
 assert_matches_seq(it, [1])
+
+# itertools.filterfalse
+it = itertools.filterfalse(lambda x: x%2, range(10))
+assert 0 == next(it)
+assert 2 == next(it)
+assert 4 == next(it)
+assert 6 == next(it)
+assert 8 == next(it)
+with assertRaises(StopIteration):
+    next(it)
+
+l = [0, 1, None, False, True, [], {}]
+it = itertools.filterfalse(None, l)
+assert 0 == next(it)
+assert None == next(it)
+assert False == next(it)
+assert [] == next(it)
+assert {} == next(it)

vm/src/stdlib/itertools.rs

@@ -418,6 +418,64 @@ impl PyItertoolsIslice {
     }
 }
 
+#[pyclass]
+#[derive(Debug)]
+struct PyItertoolsFilterFalse {
+    predicate: PyObjectRef,
+    iterable: PyObjectRef,
+}
+
+impl PyValue for PyItertoolsFilterFalse {
+    fn class(vm: &VirtualMachine) -> PyClassRef {
+        vm.class("itertools", "filterfalse")
+    }
+}
+
+#[pyimpl]
+impl PyItertoolsFilterFalse {
+    #[pymethod(name = "__new__")]
+    #[allow(clippy::new_ret_no_self)]
+    fn new(
+        _cls: PyClassRef,
+        predicate: PyObjectRef,
+        iterable: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult {
+        let iter = get_iter(vm, &iterable)?;
+
+        Ok(PyItertoolsFilterFalse {
+            predicate,
+            iterable: iter,
+        }
+        .into_ref(vm)
+        .into_object())
+    }
+
+    #[pymethod(name = "__next__")]
+    fn next(&self, vm: &VirtualMachine) -> PyResult {
+        let predicate = &self.predicate;
+        let iterable = &self.iterable;
+
+        loop {
+            let obj = call_next(vm, iterable)?;
+            let pred_value = if predicate.is(&vm.get_none()) {
+                obj.clone()
+            } else {
+                vm.invoke(predicate, vec![obj.clone()])?
+            };
+
+            if !objbool::boolval(vm, pred_value)? {
+                return Ok(obj);
+            }
+        }
+    }
+
+    #[pymethod(name = "__iter__")]
+    fn iter(zelf: PyRef<Self>, _vm: &VirtualMachine) -> PyRef<Self> {
+        zelf
+    }
+}
+
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
 
@@ -436,6 +494,9 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
 
     let islice = PyItertoolsIslice::make_class(ctx);
 
+    let filterfalse = ctx.new_class("filterfalse", ctx.object());
+    PyItertoolsFilterFalse::extend_class(ctx, &filterfalse);
+
     py_module!(vm, "itertools", {
         "chain" => chain,
         "count" => count,
@@ -443,5 +504,6 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "starmap" => starmap,
         "takewhile" => takewhile,
         "islice" => islice,
+        "filterfalse" => filterfalse,
     })
 }