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bpo-42381: Allow walrus in set literals and set comprehensions (GH-23332)

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Currently walruses are not allowerd in set literals and set comprehensions:

>>> {y := 4, 4**2, 3**3}
  File "<stdin>", line 1
    {y := 4, 4**2, 3**3}
       ^
SyntaxError: invalid syntax

but they should be allowed as well per PEP 572
This commit is contained in:
Pablo Galindo 2020-11-17 01:17:12 +00:00 • committed by GitHub
parent a57b3d30f6
commit b0aba1fcdc
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 1680 additions and 1790 deletions
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60
Lib/test/test_named_expressions.py
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@ -113,7 +113,7 @@ class NamedExpressionInvalidTest(unittest.TestCase):
"assignment expression within a comprehension cannot be used in a class body"):
exec(code, {}, {})
def test_named_expression_invalid_rebinding_comprehension_iteration_variable(self):
def test_named_expression_invalid_rebinding_list_comprehension_iteration_variable(self):
cases = [
("Local reuse", 'i', "[i := 0 for i in range(5)]"),
("Nested reuse", 'j', "[[(j := 0) for i in range(5)] for j in range(5)]"),
@ -130,7 +130,7 @@ class NamedExpressionInvalidTest(unittest.TestCase):
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}, {})
def test_named_expression_invalid_rebinding_comprehension_inner_loop(self):
def test_named_expression_invalid_rebinding_list_comprehension_inner_loop(self):
cases = [
("Inner reuse", 'j', "[i for i in range(5) if (j := 0) for j in range(5)]"),
("Inner unpacking reuse", 'j', "[i for i in range(5) if (j := 0) for j, k in [(0, 1)]]"),
@ -145,7 +145,7 @@ class NamedExpressionInvalidTest(unittest.TestCase):
with self.assertRaisesRegex(SyntaxError, msg):
exec(f"lambda: {code}", {}) # Function scope
def test_named_expression_invalid_comprehension_iterable_expression(self):
def test_named_expression_invalid_list_comprehension_iterable_expression(self):
cases = [
("Top level", "[i for i in (i := range(5))]"),
("Inside tuple", "[i for i in (2, 3, i := range(5))]"),
@ -167,6 +167,60 @@ class NamedExpressionInvalidTest(unittest.TestCase):
with self.assertRaisesRegex(SyntaxError, msg):
exec(f"lambda: {code}", {}) # Function scope
def test_named_expression_invalid_rebinding_set_comprehension_iteration_variable(self):
cases = [
("Local reuse", 'i', "{i := 0 for i in range(5)}"),
("Nested reuse", 'j', "{{(j := 0) for i in range(5)} for j in range(5)}"),
("Reuse inner loop target", 'j', "{(j := 0) for i in range(5) for j in range(5)}"),
("Unpacking reuse", 'i', "{i := 0 for i, j in {(0, 1)}}"),
("Reuse in loop condition", 'i', "{i+1 for i in range(5) if (i := 0)}"),
("Unreachable reuse", 'i', "{False or (i:=0) for i in range(5)}"),
("Unreachable nested reuse", 'i',
"{(i, j) for i in range(5) for j in range(5) if True or (i:=10)}"),
]
for case, target, code in cases:
msg = f"assignment expression cannot rebind comprehension iteration variable '{target}'"
with self.subTest(case=case):
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}, {})
def test_named_expression_invalid_rebinding_set_comprehension_inner_loop(self):
cases = [
("Inner reuse", 'j', "{i for i in range(5) if (j := 0) for j in range(5)}"),
("Inner unpacking reuse", 'j', "{i for i in range(5) if (j := 0) for j, k in {(0, 1)}}"),
]
for case, target, code in cases:
msg = f"comprehension inner loop cannot rebind assignment expression target '{target}'"
with self.subTest(case=case):
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}) # Module scope
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}, {}) # Class scope
with self.assertRaisesRegex(SyntaxError, msg):
exec(f"lambda: {code}", {}) # Function scope
def test_named_expression_invalid_set_comprehension_iterable_expression(self):
cases = [
("Top level", "{i for i in (i := range(5))}"),
("Inside tuple", "{i for i in (2, 3, i := range(5))}"),
("Inside list", "{i for i in {2, 3, i := range(5)}}"),
("Different name", "{i for i in (j := range(5))}"),
("Lambda expression", "{i for i in (lambda:(j := range(5)))()}"),
("Inner loop", "{i for i in range(5) for j in (i := range(5))}"),
("Nested comprehension", "{i for i in {j for j in (k := range(5))}}"),
("Nested comprehension condition", "{i for i in {j for j in range(5) if (j := True)}}"),
("Nested comprehension body", "{i for i in {(j := True) for j in range(5)}}"),
]
msg = "assignment expression cannot be used in a comprehension iterable expression"
for case, code in cases:
with self.subTest(case=case):
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}) # Module scope
with self.assertRaisesRegex(SyntaxError, msg):
exec(code, {}, {}) # Class scope
with self.assertRaisesRegex(SyntaxError, msg):
exec(f"lambda: {code}", {}) # Function scope
class NamedExpressionAssignmentTest(unittest.TestCase):