reject wide-mode with different types

Author: nicolaskruchten

packages/python/plotly/plotly/express/_core.py

@@ -1329,6 +1329,14 @@ def build_dataframe(args, constructor):
         else:
             wide_cross_name = args["wide_cross"]
         del args["wide_cross"]
+        dtype = None
+        for v in wide_value_vars:
+            if dtype is None:
+                dtype = df_output[v].dtype
+            elif dtype != df_output[v].dtype:
+                raise ValueError(
+                    "Plotly Express cannot process wide-form data with columns of different type."
+                )
         df_output = df_output.melt(
             id_vars=wide_id_vars,
             value_vars=wide_value_vars,

packages/python/plotly/plotly/tests/test_core/test_px/test_px_wide.py

@@ -710,3 +710,13 @@ def test_multi_index():
     with pytest.raises(TypeError) as err_msg:
         px.scatter(df)
     assert "pandas MultiIndex is not supported by plotly express" in str(err_msg.value)
+
+
+@pytest.mark.parametrize("df", [px.data.stocks(), dict(a=[1, 2], b=["1", "2"])])
+def test_mixed_input_error(df):
+    with pytest.raises(ValueError) as err_msg:
+        px.line(df)
+    assert (
+        "Plotly Express cannot process wide-form data with columns of different type"
+        in str(err_msg.value)
+    )