Method test_listcomps

Lib/test/test_grammar.py:1670–1731

(self)

        self.assertEqual({i:i+1 for i in nums}, {1: 2, 2: 3, 3: 4})

    def test_listcomps(self):
        # list comprehension tests
        nums = [1, 2, 3, 4, 5]
        strs = ["Apple", "Banana", "Coconut"]
        spcs = ["  Apple", " Banana ", "Coco  nut  "]

        self.assertEqual([s.strip() for s in spcs], ['Apple', 'Banana', 'Coco  nut'])
        self.assertEqual([3 * x for x in nums], [3, 6, 9, 12, 15])
        self.assertEqual([x for x in nums if x > 2], [3, 4, 5])
        self.assertEqual([(i, s) for i in nums for s in strs],
                         [(1, 'Apple'), (1, 'Banana'), (1, 'Coconut'),
                          (2, 'Apple'), (2, 'Banana'), (2, 'Coconut'),
                          (3, 'Apple'), (3, 'Banana'), (3, 'Coconut'),
                          (4, 'Apple'), (4, 'Banana'), (4, 'Coconut'),
                          (5, 'Apple'), (5, 'Banana'), (5, 'Coconut')])
        self.assertEqual([(i, s) for i in nums for s in [f for f in strs if "n" in f]],
                         [(1, 'Banana'), (1, 'Coconut'), (2, 'Banana'), (2, 'Coconut'),
                          (3, 'Banana'), (3, 'Coconut'), (4, 'Banana'), (4, 'Coconut'),
                          (5, 'Banana'), (5, 'Coconut')])
        self.assertEqual([(lambda a:[a**i for i in range(a+1)])(j) for j in range(5)],
                         [[1], [1, 1], [1, 2, 4], [1, 3, 9, 27], [1, 4, 16, 64, 256]])

        def test_in_func(l):
            return [0 < x < 3 for x in l if x > 2]

        self.assertEqual(test_in_func(nums), [False, False, False])

        def test_nested_front():
            self.assertEqual([[y for y in [x, x + 1]] for x in [1,3,5]],
                             [[1, 2], [3, 4], [5, 6]])

        test_nested_front()

        check_syntax_error(self, "[i, s for i in nums for s in strs]")
        check_syntax_error(self, "[x if y]")

        suppliers = [
          (1, "Boeing"),
          (2, "Ford"),
          (3, "Macdonalds")
        ]

        parts = [
          (10, "Airliner"),
          (20, "Engine"),
          (30, "Cheeseburger")
        ]

        suppart = [
          (1, 10), (1, 20), (2, 20), (3, 30)
        ]

        x = [
          (sname, pname)
            for (sno, sname) in suppliers
              for (pno, pname) in parts
                for (sp_sno, sp_pno) in suppart
                  if sno == sp_sno and pno == sp_pno