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fix: tail(0, seq) should return empty instead of the whole sequence #629

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fix: tail(0, seq) should return empty instead of the whole sequence #629

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5 changes: 5 additions & 0 deletions toolz/itertoolz.py
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Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,11 @@ def tail(n, seq):
drop
take
"""
if n == 0:
try:
return seq[:0]
except (TypeError, KeyError):
return ()
try:
return seq[-n:]
except (TypeError, KeyError):
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5 changes: 5 additions & 0 deletions toolz/tests/test_itertoolz.py
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Original file line number Diff line number Diff line change
Expand Up @@ -189,6 +189,11 @@ def test_tail():
assert list(tail(3, 'ABCDE')) == list('CDE')
assert list(tail(3, iter('ABCDE'))) == list('CDE')
assert list(tail(2, (3, 2, 1))) == list((2, 1))
assert tail(0, [10, 20, 30]) == []
assert list(tail(0, [10, 20, 30])) == []
assert tuple(tail(0, iter([10, 20, 30]))) == ()
assert tail(0, 'ABCDE') == ''
assert tail(0, (3, 2, 1)) == ()


def test_drop():
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