Add array interface to define how arrays of PulseSequences are created

filter_functions/pulse_sequence.py

@@ -237,6 +237,17 @@ class PulseSequence:
     Due to the heavy use of NumPy's :func:`~numpy.einsum` function,
     results have a floating point error of ~1e-13.
     """
+    __array_interface__ = {
+        'shape': (),
+        'typestr': '|O',
+        'version': 3
+    }
+    """Describes to NumPy how to convert this object into an array.
+
+    Since :class:`PulseSequence` is iterable (through
+    :meth:`__getitem__`), NumPy would otherwise try to create an
+    ndarray of single-segment :class:`PulseSequence` s.
+    """
 
     def __init__(self, *args, **kwargs) -> None:
         """Initialize a PulseSequence instance."""

tests/test_sequencing.py

@@ -100,6 +100,14 @@ def test_slicing(self):
         with self.assertRaises(IndexError):
             pulse['a']
 
+    def test_array(self):
+        """Test array of PulseSequences."""
+        pulses = list(testutil.rand_pulse_sequence(2, 24)[::3])
+        array = np.array(pulses)
+
+        self.assertIs(array.dtype, np.dtype('O'))
+        self.assertEqual(array.shape, (8,))
+
     def test_concatenate_without_filter_function(self):
         """Concatenate two Spin Echos without filter functions."""
         tau = 10