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223 lines
4.8 KiB
Python
223 lines
4.8 KiB
Python
import doctest
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import unittest
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doctests = """
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Unpack tuple
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>>> t = (1, 2, 3)
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>>> a, b, c = t
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>>> a == 1 and b == 2 and c == 3
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True
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Unpack list
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>>> l = [4, 5, 6]
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>>> a, b, c = l
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>>> a == 4 and b == 5 and c == 6
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True
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Unpack dict
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>>> d = {4: 'four', 5: 'five', 6: 'six'}
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>>> a, b, c = d
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>>> a == 4 and b == 5 and c == 6
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True
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Unpack implied tuple
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>>> a, b, c = 7, 8, 9
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>>> a == 7 and b == 8 and c == 9
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True
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Unpack string... fun!
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>>> a, b, c = 'one'
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>>> a == 'o' and b == 'n' and c == 'e'
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True
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Unpack generic sequence
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>>> class Seq:
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... def __getitem__(self, i):
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... if i >= 0 and i < 3: return i
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... raise IndexError
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...
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>>> a, b, c = Seq()
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>>> a == 0 and b == 1 and c == 2
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True
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Single element unpacking, with extra syntax
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>>> st = (99,)
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>>> sl = [100]
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>>> a, = st
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>>> a
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99
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>>> b, = sl
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>>> b
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100
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Now for some failures
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Unpacking non-sequence
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>>> a, b, c = 7
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Traceback (most recent call last):
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...
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TypeError: cannot unpack non-iterable int object
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Unpacking tuple of wrong size
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>>> a, b = t
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 2, got 3)
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Unpacking tuple of wrong size
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>>> a, b = l
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 2, got 3)
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Unpacking sequence too short
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>>> a, b, c, d = Seq()
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Traceback (most recent call last):
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...
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ValueError: not enough values to unpack (expected 4, got 3)
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Unpacking sequence too long
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>>> a, b = Seq()
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 2)
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Unpacking a sequence where the test for too long raises a different kind of
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error
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>>> class BozoError(Exception):
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... pass
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...
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>>> class BadSeq:
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... def __getitem__(self, i):
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... if i >= 0 and i < 3:
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... return i
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... elif i == 3:
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... raise BozoError
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... else:
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... raise IndexError
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...
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Trigger code while not expecting an IndexError (unpack sequence too long, wrong
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error)
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>>> a, b, c, d, e = BadSeq()
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Traceback (most recent call last):
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...
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test.test_unpack.BozoError
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Trigger code while expecting an IndexError (unpack sequence too short, wrong
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error)
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>>> a, b, c = BadSeq()
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Traceback (most recent call last):
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...
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test.test_unpack.BozoError
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Allow unpacking empty iterables
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>>> () = []
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>>> [] = ()
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>>> [] = []
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>>> () = ()
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Unpacking non-iterables should raise TypeError
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>>> () = 42
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Traceback (most recent call last):
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...
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TypeError: cannot unpack non-iterable int object
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Unpacking to an empty iterable should raise ValueError
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>>> () = [42]
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 0, got 1)
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Unpacking a larger iterable should raise ValuleError, but it
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should not entirely consume the iterable
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>>> it = iter(range(100))
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>>> x, y, z = it
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 3)
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>>> next(it)
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4
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Unpacking unbalanced dict
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>>> d = {4: 'four', 5: 'five', 6: 'six', 7: 'seven'}
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>>> a, b, c = d
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 3, got 4)
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Ensure that custom `__len__()` is NOT called when showing the error message
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>>> class LengthTooLong:
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... def __len__(self):
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... return 5
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... def __getitem__(self, i):
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... return i*2
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...
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>>> x, y, z = LengthTooLong()
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 3)
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For evil cases like these as well, no actual count to be shown
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>>> class BadLength:
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... def __len__(self):
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... return 1
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... def __getitem__(self, i):
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... return i*2
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...
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>>> x, y, z = BadLength()
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Traceback (most recent call last):
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...
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ValueError: too many values to unpack (expected 3)
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"""
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__test__ = {'doctests' : doctests}
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def load_tests(loader, tests, pattern):
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tests.addTest(doctest.DocTestSuite())
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return tests
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class TestCornerCases(unittest.TestCase):
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def test_extended_oparg_not_ignored(self):
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# https://github.com/python/cpython/issues/91625
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target = "(" + "y,"*400 + ")"
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code = f"""def unpack_400(x):
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{target} = x
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return y
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"""
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ns = {}
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exec(code, ns)
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unpack_400 = ns["unpack_400"]
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# Warm up the function for quickening (PEP 659)
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for _ in range(30):
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y = unpack_400(range(400))
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self.assertEqual(y, 399)
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if __name__ == "__main__":
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unittest.main()
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