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412 lines
10 KiB
Python
412 lines
10 KiB
Python
# Tests for extended unpacking, starred expressions.
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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 = l
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>>> a == 4 and b == [5, 6]
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True
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Unpack implied tuple
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>>> *a, = 7, 8, 9
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>>> a == [7, 8, 9]
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True
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Unpack nested implied tuple
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>>> [*[*a]] = [[7,8,9]]
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>>> a == [[7,8,9]]
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True
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Unpack string... fun!
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>>> a, *b = 'one'
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>>> a == 'o' and b == ['n', 'e']
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True
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Unpack long sequence
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>>> a, b, c, *d, e, f, g = range(10)
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>>> (a, b, c, d, e, f, g) == (0, 1, 2, [3, 4, 5, 6], 7, 8, 9)
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True
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Unpack short sequence
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>>> a, *b, c = (1, 2)
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>>> a == 1 and c == 2 and b == []
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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 = Seq()
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>>> a == 0 and b == [1, 2]
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True
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Unpack in for statement
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>>> for a, *b, c in [(1,2,3), (4,5,6,7)]:
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... print(a, b, c)
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...
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1 [2] 3
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4 [5, 6] 7
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Unpack in list
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>>> [a, *b, c] = range(5)
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>>> a == 0 and b == [1, 2, 3] and c == 4
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True
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Multiple targets
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>>> a, *b, c = *d, e = range(5)
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>>> a == 0 and b == [1, 2, 3] and c == 4 and d == [0, 1, 2, 3] and e == 4
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True
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Assignment unpacking
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>>> a, b, *c = range(5)
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>>> a, b, c
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(0, 1, [2, 3, 4])
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>>> *a, b, c = a, b, *c
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>>> a, b, c
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([0, 1, 2], 3, 4)
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Set display element unpacking
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>>> a = [1, 2, 3]
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>>> sorted({1, *a, 0, 4})
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[0, 1, 2, 3, 4]
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>>> {1, *1, 0, 4}
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Traceback (most recent call last):
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...
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TypeError: 'int' object is not iterable
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Dict display element unpacking
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>>> kwds = {'z': 0, 'w': 12}
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>>> sorted({'x': 1, 'y': 2, **kwds}.items())
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[('w', 12), ('x', 1), ('y', 2), ('z', 0)]
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>>> sorted({**{'x': 1}, 'y': 2, **{'z': 3}}.items())
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[('x', 1), ('y', 2), ('z', 3)]
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>>> sorted({**{'x': 1}, 'y': 2, **{'x': 3}}.items())
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[('x', 3), ('y', 2)]
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>>> sorted({**{'x': 1}, **{'x': 3}, 'x': 4}.items())
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[('x', 4)]
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>>> {**{}}
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{}
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>>> a = {}
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>>> {**a}[0] = 1
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>>> a
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{}
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>>> {**1}
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Traceback (most recent call last):
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...
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TypeError: 'int' object is not a mapping
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>>> {**[]}
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Traceback (most recent call last):
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...
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TypeError: 'list' object is not a mapping
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>>> len(eval("{" + ", ".join("**{{{}: {}}}".format(i, i)
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... for i in range(1000)) + "}"))
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1000
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>>> {0:1, **{0:2}, 0:3, 0:4}
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{0: 4}
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List comprehension element unpacking
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>>> a, b, c = [0, 1, 2], 3, 4
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>>> [*a, b, c]
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[0, 1, 2, 3, 4]
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>>> l = [a, (3, 4), {5}, {6: None}, (i for i in range(7, 10))]
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>>> [*item for item in l]
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Traceback (most recent call last):
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...
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SyntaxError: iterable unpacking cannot be used in comprehension
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>>> [*[0, 1] for i in range(10)]
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Traceback (most recent call last):
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...
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SyntaxError: iterable unpacking cannot be used in comprehension
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>>> [*'a' for i in range(10)]
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Traceback (most recent call last):
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...
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SyntaxError: iterable unpacking cannot be used in comprehension
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>>> [*[] for i in range(10)]
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Traceback (most recent call last):
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...
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SyntaxError: iterable unpacking cannot be used in comprehension
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>>> {**{} for a in [1]}
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Traceback (most recent call last):
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...
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SyntaxError: dict unpacking cannot be used in dict comprehension
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# Pegen is better here.
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# Generator expression in function arguments
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# >>> list(*x for x in (range(5) for i in range(3)))
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# Traceback (most recent call last):
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# ...
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# list(*x for x in (range(5) for i in range(3)))
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# ^
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# SyntaxError: invalid syntax
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>>> dict(**x for x in [{1:2}])
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Traceback (most recent call last):
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...
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dict(**x for x in [{1:2}])
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^
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SyntaxError: invalid syntax
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Iterable argument unpacking
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>>> print(*[1], *[2], 3)
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1 2 3
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Make sure that they don't corrupt the passed-in dicts.
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>>> def f(x, y):
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... print(x, y)
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...
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>>> original_dict = {'x': 1}
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>>> f(**original_dict, y=2)
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1 2
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>>> original_dict
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{'x': 1}
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Now for some failures
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Make sure the raised errors are right for keyword argument unpackings
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>>> from collections.abc import MutableMapping
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>>> class CrazyDict(MutableMapping):
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... def __init__(self):
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... self.d = {}
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...
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... def __iter__(self):
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... for x in self.d.__iter__():
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... if x == 'c':
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... self.d['z'] = 10
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... yield x
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...
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... def __getitem__(self, k):
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... return self.d[k]
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...
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... def __len__(self):
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... return len(self.d)
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...
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... def __setitem__(self, k, v):
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... self.d[k] = v
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...
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... def __delitem__(self, k):
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... del self.d[k]
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...
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>>> d = CrazyDict()
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>>> d.d = {chr(ord('a') + x): x for x in range(5)}
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>>> e = {**d}
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Traceback (most recent call last):
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...
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RuntimeError: dictionary changed size during iteration
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>>> d.d = {chr(ord('a') + x): x for x in range(5)}
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>>> def f(**kwargs): print(kwargs)
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>>> f(**d)
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Traceback (most recent call last):
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...
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RuntimeError: dictionary changed size during iteration
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Overridden parameters
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>>> f(x=5, **{'x': 3}, y=2)
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Traceback (most recent call last):
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...
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TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
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>>> f(**{'x': 3}, x=5, y=2)
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Traceback (most recent call last):
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...
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TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
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>>> f(**{'x': 3}, **{'x': 5}, y=2)
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Traceback (most recent call last):
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...
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TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
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>>> f(x=5, **{'x': 3}, **{'x': 2})
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Traceback (most recent call last):
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...
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TypeError: test.test_unpack_ex.f() got multiple values for keyword argument 'x'
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>>> f(**{1: 3}, **{1: 5})
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Traceback (most recent call last):
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...
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TypeError: test.test_unpack_ex.f() got multiple values for keyword argument '1'
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Unpacking non-sequence
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>>> a, *b = 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 sequence too short
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>>> a, *b, c, d, e = 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 at least 4, got 3)
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Unpacking sequence too short and target appears last
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>>> a, b, c, d, *e = 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 at least 4, got 3)
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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_ex.BozoError
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Now some general starred expressions (all fail).
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>>> a, *b, c, *d, e = range(10) # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: multiple starred expressions in assignment
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>>> [*b, *c] = range(10) # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: multiple starred expressions in assignment
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>>> a,*b,*c,*d = range(4) # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: multiple starred expressions in assignment
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>>> *a = range(10) # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: starred assignment target must be in a list or tuple
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>>> *a # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: can't use starred expression here
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>>> *1 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: can't use starred expression here
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>>> x = *a # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: can't use starred expression here
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>>> (*x),y = 1, 2 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: cannot use starred expression here
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>>> (((*x))),y = 1, 2 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: cannot use starred expression here
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>>> z,(*x),y = 1, 2, 4 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: cannot use starred expression here
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>>> z,(*x) = 1, 2 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: cannot use starred expression here
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>>> ((*x),y) = 1, 2 # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: cannot use starred expression here
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Some size constraints (all fail.)
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>>> s = ", ".join("a%d" % i for i in range(1<<8)) + ", *rest = range(1<<8 + 1)"
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>>> compile(s, 'test', 'exec') # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: too many expressions in star-unpacking assignment
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>>> s = ", ".join("a%d" % i for i in range(1<<8 + 1)) + ", *rest = range(1<<8 + 2)"
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>>> compile(s, 'test', 'exec') # doctest:+ELLIPSIS
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Traceback (most recent call last):
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...
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SyntaxError: too many expressions in star-unpacking assignment
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(there is an additional limit, on the number of expressions after the
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'*rest', but it's 1<<24 and testing it takes too much memory.)
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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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if __name__ == "__main__":
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unittest.main()
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