ARROW-12677: Changed mask logic to align with other masks. Added memo…

…ry_pool since we will invert the mask (requires an allocation) if specified. Added tests for list arrays

python/pyarrow/array.pxi

@@ -1593,6 +1593,39 @@ cdef class ListArray(BaseListArray):
         Returns
         -------
         list_array : ListArray
+
+        Examples
+        --------
+        >>> values = pa.array([1, 2, 3, 4])
+        >>> offsets = pa.array([0, 2, 4])
+        >>> pa.ListArray.from_arrays(offsets, values)
+        <pyarrow.lib.ListArray object at 0x7fbde226bf40>
+        [
+          [
+            0,
+            1
+          ],
+          [
+            2,
+            3
+          ]
+        ]
+
+        # nulls in the offsets array become null lists
+        >>> offsets = pa.array([0, None, 2, 4])
+        >>> pa.ListArray.from_arrays(offsets, values)
+        <pyarrow.lib.ListArray object at 0x7fbde226bf40>
+        [
+          [
+            0,
+            1
+          ],
+          null,
+          [
+            2,
+            3
+          ]
+        ]
         """
         cdef:
             Array _offsets, _values
@@ -2153,7 +2186,7 @@ cdef class StructArray(Array):
         return [pyarrow_wrap_array(arr) for arr in arrays]
 
     @staticmethod
-    def from_arrays(arrays, names=None, fields=None, mask=None):
+    def from_arrays(arrays, names=None, fields=None, mask=None, memory_pool=None):
         """
         Construct StructArray from collection of arrays representing
         each field in the struct.
@@ -2168,7 +2201,9 @@ cdef class StructArray(Array):
         fields : List[Field] (optional)
             Field instances for each struct child.
         mask : pyarrow.Array[bool] (optional)
-            Indicate which values are null (False) or not null (True).
+            Indicate which values are null (True) or not null (False).
+        memory_pool : MemoryPool (optional)
+            For memory allocations, if required, otherwise uses default pool.
 
         Returns
         -------
@@ -2199,7 +2234,8 @@ cdef class StructArray(Array):
                 raise ValueError('Mask must be a pyarray.Array of type bool')
             if mask.null_count != 0:
                 raise ValueError('Mask must not contain nulls')
-            c_mask = pyarrow_unwrap_buffer(mask.buffers()[1])
+            inverted_mask = _pc().invert(mask, memory_pool=memory_pool)
+            c_mask = pyarrow_unwrap_buffer(inverted_mask.buffers()[1])
         else:
             raise ValueError('Mask must be a pyarray.Array of type bool')
 

python/pyarrow/tests/test_array.py

@@ -671,7 +671,7 @@ def test_struct_from_arrays():
     arrays = [a, b, c]
     fields = [fa, fb, fc]
     # With mask
-    mask = pa.array([False, True, True])
+    mask = pa.array([True, False, False])
     arr = pa.StructArray.from_arrays(arrays, fields=fields, mask=mask)
     assert arr.to_pylist() == [None] + expected_list[1:]
 
@@ -954,6 +954,24 @@ def test_fixed_size_list_from_arrays():
         pa.FixedSizeListArray.from_arrays(values, 5)
 
 
+def test_variable_list_from_arrays():
+    values = pa.array([1, 2, 3, 4], pa.int64())
+    offsets = pa.array([0, 2, 4])
+    result = pa.ListArray.from_arrays(offsets, values)
+    assert result.to_pylist() == [[1, 2], [3, 4]]
+    assert result.type.equals(pa.list_(pa.int64()))
+
+    offsets = pa.array([0, None, 2, 4])
+    result = pa.ListArray.from_arrays(offsets, values)
+    assert result.to_pylist() == [[1, 2], None, [3, 4]]
+
+    # raise if offset out of bounds
+    with pytest.raises(ValueError):
+        pa.ListArray.from_arrays(pa.array([-1, 2, 4]), values)
+
+    with pytest.raises(ValueError):
+        pa.ListArray.from_arrays(pa.array([0, 2, 5]), values)
+
 def test_union_from_dense():
     binary = pa.array([b'a', b'b', b'c', b'd'], type='binary')
     int64 = pa.array([1, 2, 3], type='int64')