mirror of https://github.com/python/cpython
158 lines
3.4 KiB
Python
158 lines
3.4 KiB
Python
# Tests for extended unpacking, starred expressions.
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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 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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Now for some failures
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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: 'int' object is not iterable
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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: need more than 3 values to unpack
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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: two 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: two 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 use starred expression only as assignment target (...)
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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 use starred expression only as assignment target (...)
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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 use starred expression only as assignment target (...)
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"""
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__test__ = {'doctests' : doctests}
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def test_main(verbose=False):
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import sys
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from test import test_support
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from test import test_unpack_ex
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test_support.run_doctest(test_unpack_ex, verbose)
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if __name__ == "__main__":
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test_main(verbose=True)
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