Better error message for DataFrame.hist() without numerical columns (pandas-dev#10444)

Author: matsmaiwald

pandas/tests/plotting/test_hist_method.py

@@ -209,6 +209,16 @@ def test_hist_df_legacy(self):
         with pytest.raises(AttributeError):
             ser.hist(foo='bar')
 
+    @pytest.mark.slow
+    def test_hist_non_numerical(self):
+        # check non-numerical df raises appropriate exception and error message
+        df = DataFrame(np.random.rand(10, 2))
+        df_o = df.astype(np.object)
+
+        msg = "hist method requires numerical columns, nothing to plot."
+        with pytest.raises(ValueError, match=msg):
+            df_o.hist()
+
     @pytest.mark.slow
     def test_hist_layout(self):
         df = DataFrame(randn(100, 3))