🥅 raise more specific error if dict is appended to frame without ignore_index

Author: Marco Gorelli

doc/source/whatsnew/v1.0.0.rst

@@ -1189,6 +1189,8 @@ Other
 - Bug where :meth:`DataFrame.itertuples` would incorrectly determine whether or not namedtuples could be used for dataframes of 255 columns (:issue:`28282`)
 - Handle nested NumPy ``object`` arrays in :func:`testing.assert_series_equal` for ExtensionArray implementations (:issue:`30841`)
 - Bug in :class:`Index` constructor incorrectly allowing 2-dimensional input arrays (:issue:`13601`, :issue:`27125`)
+- Appending a dictionary to a :class:`DataFrame` without passing ``ignore_index=True`` will raise ``TypeError: Can only append a dict if ignore_index=True``
+  instead of ``TypeError: Can only append a Series if ignore_index=True or if the Series has a name`` (:issue`30871`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/frame.py

@@ -7062,6 +7062,8 @@ def append(
         """
         if isinstance(other, (Series, dict)):
             if isinstance(other, dict):
+                if not ignore_index:
+                    raise TypeError("Can only append a dict if ignore_index=True")
                 other = Series(other)
             if other.name is None and not ignore_index:
                 raise TypeError(

pandas/tests/frame/methods/test_append.py

@@ -50,6 +50,10 @@ def test_append_series_dict(self):
         )
         tm.assert_frame_equal(result, expected.loc[:, result.columns])
 
+        msg = "Can only append a dict if ignore_index=True"
+        with pytest.raises(TypeError, match=msg):
+            df.append(series.to_dict())
+
         # can append when name set
         row = df.loc[4]
         row.name = 5