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Merged
youknowone merged 3 commits into from
Feb 1, 2026
Merged

Update test_pep646_syntax from v3.14.2 #6928

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553be2a
Update test_pep646_syntax from v3.14.2-288-g06f9c8ca1c
Feb 1, 2026
2bb027a
Mark failing tests
fanninpm Feb 1, 2026
f6d1fe4
Add `test_pep646_syntax` to platform-independent tests
fanninpm Feb 1, 2026
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Update test_pep646_syntax from v3.14.2-288-g06f9c8ca1c
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@fanninpm
CPython Developers authored and fanninpm committed Feb 1, 2026
commit 553be2af334f317f4ac73c057d5e746ecfb47ec4
329 changes: 329 additions & 0 deletions Lib/test/test_pep646_syntax.py
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import doctest
import unittest

doctests = """

Setup

>>> class AClass:
... def __init__(self):
... self._setitem_name = None
... self._setitem_val = None
... self._delitem_name = None
... def __setitem__(self, name, val):
... self._delitem_name = None
... self._setitem_name = name
... self._setitem_val = val
... def __repr__(self):
... if self._setitem_name is not None:
... return f"A[{self._setitem_name}]={self._setitem_val}"
... elif self._delitem_name is not None:
... return f"delA[{self._delitem_name}]"
... def __getitem__(self, name):
... return ParameterisedA(name)
... def __delitem__(self, name):
... self._setitem_name = None
... self._delitem_name = name
...
>>> class ParameterisedA:
... def __init__(self, name):
... self._name = name
... def __repr__(self):
... return f"A[{self._name}]"
... def __iter__(self):
... for p in self._name:
... yield p
>>> class B:
... def __iter__(self):
... yield StarredB()
... def __repr__(self):
... return "B"
>>> class StarredB:
... def __repr__(self):
... return "StarredB"
>>> A = AClass()
>>> b = B()

Slices that are supposed to work, starring our custom B class

>>> A[*b]
A[(StarredB,)]
>>> A[*b] = 1; A
A[(StarredB,)]=1
>>> del A[*b]; A
delA[(StarredB,)]

>>> A[*b, *b]
A[(StarredB, StarredB)]
>>> A[*b, *b] = 1; A
A[(StarredB, StarredB)]=1
>>> del A[*b, *b]; A
delA[(StarredB, StarredB)]

>>> A[b, *b]
A[(B, StarredB)]
>>> A[b, *b] = 1; A
A[(B, StarredB)]=1
>>> del A[b, *b]; A
delA[(B, StarredB)]

>>> A[*b, b]
A[(StarredB, B)]
>>> A[*b, b] = 1; A
A[(StarredB, B)]=1
>>> del A[*b, b]; A
delA[(StarredB, B)]

>>> A[b, b, *b]
A[(B, B, StarredB)]
>>> A[b, b, *b] = 1; A
A[(B, B, StarredB)]=1
>>> del A[b, b, *b]; A
delA[(B, B, StarredB)]

>>> A[*b, b, b]
A[(StarredB, B, B)]
>>> A[*b, b, b] = 1; A
A[(StarredB, B, B)]=1
>>> del A[*b, b, b]; A
delA[(StarredB, B, B)]

>>> A[b, *b, b]
A[(B, StarredB, B)]
>>> A[b, *b, b] = 1; A
A[(B, StarredB, B)]=1
>>> del A[b, *b, b]; A
delA[(B, StarredB, B)]

>>> A[b, b, *b, b]
A[(B, B, StarredB, B)]
>>> A[b, b, *b, b] = 1; A
A[(B, B, StarredB, B)]=1
>>> del A[b, b, *b, b]; A
delA[(B, B, StarredB, B)]

>>> A[b, *b, b, b]
A[(B, StarredB, B, B)]
>>> A[b, *b, b, b] = 1; A
A[(B, StarredB, B, B)]=1
>>> del A[b, *b, b, b]; A
delA[(B, StarredB, B, B)]

>>> A[A[b, *b, b]]
A[A[(B, StarredB, B)]]
>>> A[A[b, *b, b]] = 1; A
A[A[(B, StarredB, B)]]=1
>>> del A[A[b, *b, b]]; A
delA[A[(B, StarredB, B)]]

>>> A[*A[b, *b, b]]
A[(B, StarredB, B)]
>>> A[*A[b, *b, b]] = 1; A
A[(B, StarredB, B)]=1
>>> del A[*A[b, *b, b]]; A
delA[(B, StarredB, B)]

>>> A[b, ...]
A[(B, Ellipsis)]
>>> A[b, ...] = 1; A
A[(B, Ellipsis)]=1
>>> del A[b, ...]; A
delA[(B, Ellipsis)]

>>> A[*A[b, ...]]
A[(B, Ellipsis)]
>>> A[*A[b, ...]] = 1; A
A[(B, Ellipsis)]=1
>>> del A[*A[b, ...]]; A
delA[(B, Ellipsis)]

Slices that are supposed to work, starring a list

>>> l = [1, 2, 3]

>>> A[*l]
A[(1, 2, 3)]
>>> A[*l] = 1; A
A[(1, 2, 3)]=1
>>> del A[*l]; A
delA[(1, 2, 3)]

>>> A[*l, 4]
A[(1, 2, 3, 4)]
>>> A[*l, 4] = 1; A
A[(1, 2, 3, 4)]=1
>>> del A[*l, 4]; A
delA[(1, 2, 3, 4)]

>>> A[0, *l]
A[(0, 1, 2, 3)]
>>> A[0, *l] = 1; A
A[(0, 1, 2, 3)]=1
>>> del A[0, *l]; A
delA[(0, 1, 2, 3)]

>>> A[1:2, *l]
A[(slice(1, 2, None), 1, 2, 3)]
>>> A[1:2, *l] = 1; A
A[(slice(1, 2, None), 1, 2, 3)]=1
>>> del A[1:2, *l]; A
delA[(slice(1, 2, None), 1, 2, 3)]

>>> repr(A[1:2, *l]) == repr(A[1:2, 1, 2, 3])
True

Slices that are supposed to work, starring a tuple

>>> t = (1, 2, 3)

>>> A[*t]
A[(1, 2, 3)]
>>> A[*t] = 1; A
A[(1, 2, 3)]=1
>>> del A[*t]; A
delA[(1, 2, 3)]

>>> A[*t, 4]
A[(1, 2, 3, 4)]
>>> A[*t, 4] = 1; A
A[(1, 2, 3, 4)]=1
>>> del A[*t, 4]; A
delA[(1, 2, 3, 4)]

>>> A[0, *t]
A[(0, 1, 2, 3)]
>>> A[0, *t] = 1; A
A[(0, 1, 2, 3)]=1
>>> del A[0, *t]; A
delA[(0, 1, 2, 3)]

>>> A[1:2, *t]
A[(slice(1, 2, None), 1, 2, 3)]
>>> A[1:2, *t] = 1; A
A[(slice(1, 2, None), 1, 2, 3)]=1
>>> del A[1:2, *t]; A
delA[(slice(1, 2, None), 1, 2, 3)]

>>> repr(A[1:2, *t]) == repr(A[1:2, 1, 2, 3])
True

Starring an expression (rather than a name) in a slice

>>> def returns_list():
... return [1, 2, 3]

>>> A[returns_list()]
A[[1, 2, 3]]
>>> A[returns_list()] = 1; A
A[[1, 2, 3]]=1
>>> del A[returns_list()]; A
delA[[1, 2, 3]]

>>> A[returns_list(), 4]
A[([1, 2, 3], 4)]
>>> A[returns_list(), 4] = 1; A
A[([1, 2, 3], 4)]=1
>>> del A[returns_list(), 4]; A
delA[([1, 2, 3], 4)]

>>> A[*returns_list()]
A[(1, 2, 3)]
>>> A[*returns_list()] = 1; A
A[(1, 2, 3)]=1
>>> del A[*returns_list()]; A
delA[(1, 2, 3)]

>>> A[*returns_list(), 4]
A[(1, 2, 3, 4)]
>>> A[*returns_list(), 4] = 1; A
A[(1, 2, 3, 4)]=1
>>> del A[*returns_list(), 4]; A
delA[(1, 2, 3, 4)]

>>> A[0, *returns_list()]
A[(0, 1, 2, 3)]
>>> A[0, *returns_list()] = 1; A
A[(0, 1, 2, 3)]=1
>>> del A[0, *returns_list()]; A
delA[(0, 1, 2, 3)]

>>> A[*returns_list(), *returns_list()]
A[(1, 2, 3, 1, 2, 3)]
>>> A[*returns_list(), *returns_list()] = 1; A
A[(1, 2, 3, 1, 2, 3)]=1
>>> del A[*returns_list(), *returns_list()]; A
delA[(1, 2, 3, 1, 2, 3)]

Using both a starred object and a start:stop in a slice
(See also tests in test_syntax confirming that starring *inside* a start:stop
is *not* valid syntax.)

>>> A[1:2, *b]
A[(slice(1, 2, None), StarredB)]
>>> A[*b, 1:2]
A[(StarredB, slice(1, 2, None))]
>>> A[1:2, *b, 1:2]
A[(slice(1, 2, None), StarredB, slice(1, 2, None))]
>>> A[*b, 1:2, *b]
A[(StarredB, slice(1, 2, None), StarredB)]

>>> A[1:, *b]
A[(slice(1, None, None), StarredB)]
>>> A[*b, 1:]
A[(StarredB, slice(1, None, None))]
>>> A[1:, *b, 1:]
A[(slice(1, None, None), StarredB, slice(1, None, None))]
>>> A[*b, 1:, *b]
A[(StarredB, slice(1, None, None), StarredB)]

>>> A[:1, *b]
A[(slice(None, 1, None), StarredB)]
>>> A[*b, :1]
A[(StarredB, slice(None, 1, None))]
>>> A[:1, *b, :1]
A[(slice(None, 1, None), StarredB, slice(None, 1, None))]
>>> A[*b, :1, *b]
A[(StarredB, slice(None, 1, None), StarredB)]

>>> A[:, *b]
A[(slice(None, None, None), StarredB)]
>>> A[*b, :]
A[(StarredB, slice(None, None, None))]
>>> A[:, *b, :]
A[(slice(None, None, None), StarredB, slice(None, None, None))]
>>> A[*b, :, *b]
A[(StarredB, slice(None, None, None), StarredB)]

*args annotated as starred expression

>>> def f1(*args: *b): pass
>>> f1.__annotations__
{'args': StarredB}

>>> def f2(*args: *b, arg1): pass
>>> f2.__annotations__
{'args': StarredB}

>>> def f3(*args: *b, arg1: int): pass
>>> f3.__annotations__
{'args': StarredB, 'arg1': <class 'int'>}

>>> def f4(*args: *b, arg1: int = 2): pass
>>> f4.__annotations__
{'args': StarredB, 'arg1': <class 'int'>}

>>> def f5(*args: *b = (1,)): pass
Traceback (most recent call last):
...
SyntaxError: invalid syntax
"""

__test__ = {'doctests' : doctests}

def load_tests(loader, tests, pattern):
tests.addTest(doctest.DocTestSuite())
return tests


if __name__ == "__main__":
unittest.main()