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import unittest
from first import first
isbool = lambda x: isinstance(x, bool)
isint = lambda x: isinstance(x, int)
odd = lambda x: isint(x) and x % 2 != 0
even = lambda x: isint(x) and x % 2 == 0
is_meaning_of_life = lambda x: x == 42
class TestFirst(unittest.TestCase):
def test_empty_iterables(self):
s = set()
l = []
assert first(s) is None
assert first(l) is None
def test_default_value(self):
s = set()
l = []
assert first(s, default=42) == 42
assert first(l, default=3.14) == 3.14
l = [0, False, []]
assert first(l, default=3.14) == 3.14
def test_selection(self):
l = [(), 0, False, 3, []]
assert first(l, default=42) == 3
assert first(l, key=isint) == 0
assert first(l, key=isbool) is False
assert first(l, key=odd) == 3
assert first(l, key=even) == 0
assert first(l, key=is_meaning_of_life) is None
if __name__ == '__main__':
unittest.main()
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