bpo-42316: Allow unparenthesized walrus operator in indexes (GH-23317)
diff --git a/Grammar/python.gram b/Grammar/python.gram
index 91ce520..a0e9a89 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -491,7 +491,7 @@
| a[asdl_expr_seq*]=','.slice+ [','] { _Py_Tuple(a, Load, EXTRA) }
slice[expr_ty]:
| a=[expression] ':' b=[expression] c=[':' d=[expression] { d }] { _Py_Slice(a, b, c, EXTRA) }
- | a=expression { a }
+ | a=named_expression { a }
atom[expr_ty]:
| NAME
| 'True' { _Py_Constant(Py_True, NULL, EXTRA) }
diff --git a/Lib/test/test_named_expressions.py b/Lib/test/test_named_expressions.py
index d614f32..9c9a58e 100644
--- a/Lib/test/test_named_expressions.py
+++ b/Lib/test/test_named_expressions.py
@@ -271,6 +271,27 @@ def test_named_expression_assignment_16(self):
fib = {(c := a): (a := b) + (b := a + c) - b for __ in range(6)}
self.assertEqual(fib, {1: 2, 2: 3, 3: 5, 5: 8, 8: 13, 13: 21})
+ def test_named_expression_assignment_17(self):
+ a = [1]
+ element = a[b:=0]
+ self.assertEqual(b, 0)
+ self.assertEqual(element, a[0])
+
+ def test_named_expression_assignment_18(self):
+ class TwoDimensionalList:
+ def __init__(self, two_dimensional_list):
+ self.two_dimensional_list = two_dimensional_list
+
+ def __getitem__(self, index):
+ return self.two_dimensional_list[index[0]][index[1]]
+
+ a = TwoDimensionalList([[1], [2]])
+ element = a[b:=0, c:=0]
+ self.assertEqual(b, 0)
+ self.assertEqual(c, 0)
+ self.assertEqual(element, a.two_dimensional_list[b][c])
+
+
class NamedExpressionScopeTest(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-30-03.bpo-42316._DdmpQ.rst b/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-30-03.bpo-42316._DdmpQ.rst
new file mode 100644
index 0000000..77eb666
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-30-03.bpo-42316._DdmpQ.rst
@@ -0,0 +1 @@
+Allow an unparenthesized walrus in subscript indexes.
\ No newline at end of file
diff --git a/Parser/parser.c b/Parser/parser.c
index 94e2658..2f6d68f 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -10639,7 +10639,7 @@ slices_rule(Parser *p)
return _res;
}
-// slice: expression? ':' expression? [':' expression?] | expression
+// slice: expression? ':' expression? [':' expression?] | named_expression
static expr_ty
slice_rule(Parser *p)
{
@@ -10701,18 +10701,18 @@ slice_rule(Parser *p)
D(fprintf(stderr, "%*c%s slice[%d-%d]: %s failed!\n", p->level, ' ',
p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "expression? ':' expression? [':' expression?]"));
}
- { // expression
+ { // named_expression
if (p->error_indicator) {
D(p->level--);
return NULL;
}
- D(fprintf(stderr, "%*c> slice[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "expression"));
+ D(fprintf(stderr, "%*c> slice[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "named_expression"));
expr_ty a;
if (
- (a = expression_rule(p)) // expression
+ (a = named_expression_rule(p)) // named_expression
)
{
- D(fprintf(stderr, "%*c+ slice[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "expression"));
+ D(fprintf(stderr, "%*c+ slice[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "named_expression"));
_res = a;
if (_res == NULL && PyErr_Occurred()) {
p->error_indicator = 1;
@@ -10723,7 +10723,7 @@ slice_rule(Parser *p)
}
p->mark = _mark;
D(fprintf(stderr, "%*c%s slice[%d-%d]: %s failed!\n", p->level, ' ',
- p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "expression"));
+ p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "named_expression"));
}
_res = NULL;
done: