Add NestSeriesAccessor.list_lengths

Author: hombit

src/nested_pandas/series/accessor.py

@@ -114,6 +114,11 @@ def to_flat(self, fields: list[str] | None = None) -> pd.DataFrame:
 
         return pd.DataFrame(flat_series)
 
+    @property
+    def list_lengths(self) -> np.ndarray:
+        """Lengths of the list arrays"""
+        return self._series.array.list_lengths
+
     @property
     def flat_length(self) -> int:
         """Length of the flat arrays"""

tests/nested_pandas/series/test_accessor.py

@@ -286,6 +286,19 @@ def test_fields():
     assert_array_equal(series.nest.fields, ["a", "b"])
 
 
+def test_list_lengths():
+    """Test that the .nest.list_lengths attribute works."""
+    series = pack_seq(
+        [
+            pd.DataFrame({"a": [1, 2, 3], "b": [1.0, 5.0, 6.0], "c": ["a", "b", "c"]}),
+            None,
+            pd.DataFrame({"a": [1, 2], "b": [None, 0.0], "c": ["a", "b"]}),
+        ]
+    )
+    assert series.shape == (3,)
+    assert series.nest.list_lengths == [3, 0, 2]
+
+
 def test_flat_length():
     """Test that the .nest.flat_length attribute works."""
     struct_array = pa.StructArray.from_arrays(