EHN: Improve from_items error message (pandas-dev#17312)

Author: reidy-p

pandas/core/frame.py

@@ -1256,6 +1256,13 @@ def from_items(cls, items, columns=None, orient='columns'):
         """
         keys, values = lzip(*items)
 
+        import array
+        for val in values:
+            if not isinstance(val, (list, Series, np.ndarray, Categorical,
+                                    array.array)):
+                raise TypeError('The value in each (key, value) pair must '
+                                'be an array or a Series')
+
         if orient == 'columns':
             if columns is not None:
                 columns = _ensure_index(columns)

pandas/tests/frame/test_constructors.py

@@ -1205,6 +1205,12 @@ def test_constructor_from_items(self):
                        columns=['one', 'two', 'three'])
         tm.assert_frame_equal(rs, xp)
 
+        # GH 17312
+        with tm.assert_raises_regex(TypeError,
+                                    'The value in each \(key, value\) '
+                                    'pair must be an array or a Series'):
+            DataFrame.from_items([('A', 1), ('B', 4)])
+
     def test_constructor_mix_series_nonseries(self):
         df = DataFrame({'A': self.frame['A'],
                         'B': list(self.frame['B'])}, columns=['A', 'B'])