BUG: User-facing AssertionError with add column to SparseDataFrame (#25503)

Author: charlesdong1991

doc/source/whatsnew/v0.25.0.rst

@@ -402,7 +402,7 @@ Sparse
 
 - Significant speedup in `SparseArray` initialization that benefits most operations, fixing performance regression introduced in v0.20.0 (:issue:`24985`)
 - Bug in :class:`SparseFrame` constructor where passing ``None`` as the data would cause ``default_fill_value`` to be ignored (:issue:`16807`)
--
+- Bug in `SparseDataFrame` when adding a column in which the length of values does not match length of index, ``AssertionError`` is raised instead of raising ``ValueError`` (:issue:`25484`)
 
 
 Other

pandas/core/sparse/frame.py

@@ -430,8 +430,8 @@ def sp_maker(x, index=None):
 
         elif isinstance(value, SparseArray):
             if len(value) != len(self.index):
-                raise AssertionError('Length of values does not match '
-                                     'length of index')
+                raise ValueError('Length of values does not match '
+                                 'length of index')
             clean = value
 
         elif hasattr(value, '__iter__'):
@@ -441,8 +441,8 @@ def sp_maker(x, index=None):
                     clean = sp_maker(clean)
             else:
                 if len(value) != len(self.index):
-                    raise AssertionError('Length of values does not match '
-                                         'length of index')
+                    raise ValueError('Length of values does not match '
+                                     'length of index')
                 clean = sp_maker(value)
 
         # Scalar

pandas/tests/sparse/frame/test_frame.py

@@ -568,8 +568,9 @@ def _check_frame(frame, orig):
             assert len(frame['I'].sp_values) == N // 2
 
             # insert ndarray wrong size
-            msg = "Length of values does not match length of index"
-            with pytest.raises(AssertionError, match=msg):
+            # GH 25484
+            msg = 'Length of values does not match length of index'
+            with pytest.raises(ValueError, match=msg):
                 frame['foo'] = np.random.randn(N - 1)
 
             # scalar value