Add lint changes

qiskit/primitives/containers/bit_array.py

@@ -134,7 +134,7 @@ def num_shots(self) -> int:
     @staticmethod
     def _bytes_to_bitstring(data: bytes, num_bits: int, mask: int) -> str:
         val = int.from_bytes(data, "big") & mask
-        return bin(val)[2:].zfill(num_bits)
+        return bin(val)[2:].zfill(num_bits) if mask else ""
 
     @staticmethod
     def _bytes_to_int(data: bytes, mask: int) -> int:
@@ -143,7 +143,13 @@ def _bytes_to_int(data: bytes, mask: int) -> int:
     def _get_counts(
         self, *, loc: int | tuple[int, ...] | None, converter: Callable[[bytes], str | int]
     ) -> dict[str, int] | dict[int, int]:
-        arr = self._array.reshape(-1, self._array.shape[-1]) if loc is None else self._array[loc]
+        if loc is None:
+            _order = self._array.shape[-1]
+            arr = self._array.reshape(-1, _order) if _order else self._array
+        else:
+            arr = self._array[loc]
+            if isinstance(arr, np.uint8):
+                arr = np.array([self._array[loc]])
 
         counts = defaultdict(int)
         for shot_row in arr:

test/python/primitives/containers/test_bit_array.py

@@ -85,6 +85,19 @@ def test_get_counts(self):
         # test that providing no location takes the union over all shots
         self.assertEqual(bit_array.get_counts(), {bs1: 2, bs2: 1, bs3: 1, bs4: 2})
 
+        bit_array = BitArray(np.zeros([1024, 2], dtype=np.uint8), num_bits=16)
+        bs5 = "00000000" + "00000000"
+        self.assertEqual(bit_array.get_counts(), {bs5: 1024})
+        self.assertEqual(bit_array.get_counts(1), {bs5: 2})
+        self.assertEqual(bit_array.get_counts((0, 1)), {bs5: 1})
+
+        # test with no classical register
+        bit_array = BitArray(np.zeros([1024, 0], dtype=np.uint8), num_bits=0)
+        self.assertEqual(bit_array.get_counts(), {"": 1024})
+        self.assertEqual(bit_array.get_counts(1), {})
+        with self.assertRaises(IndexError):
+            bit_array.get_counts((0, 1))
+
     def test_get_int_counts(self):
         """Test conversion to int counts."""
         # note that [234, 100] requires 16 bits, not 15; we are testing that get_counts ignores the
@@ -108,6 +121,19 @@ def test_get_int_counts(self):
         # test that providing no location takes the union over all shots
         self.assertEqual(bit_array.get_int_counts(), {val1: 2, val2: 1, val3: 1, val4: 2})
 
+        bit_array = BitArray(np.zeros([1024, 2], dtype=np.uint8), num_bits=16)
+        val5 = 0
+        self.assertEqual(bit_array.get_int_counts(), {val5: 1024})
+        self.assertEqual(bit_array.get_int_counts(1), {val5: 2})
+        self.assertEqual(bit_array.get_int_counts((0, 1)), {val5: 1})
+
+        # test with no classical register
+        bit_array = BitArray(np.zeros([1024, 0], dtype=np.uint8), num_bits=0)
+        self.assertEqual(bit_array.get_int_counts(), {0: 1024})
+        self.assertEqual(bit_array.get_int_counts(1), {})
+        with self.assertRaises(IndexError):
+            bit_array.get_int_counts((0, 1))
+
     def test_get_bitstrings(self):
         """Test conversion to bitstrings."""
         # note that [234, 100] requires 16 bits, not 15; we are testing that get_counts ignores the