fix: Setting category_orders was leading to missing data

Author: MarcoGorelli

Diff for: packages/python/plotly/plotly/express/_core.py

@@ -2422,7 +2422,6 @@ def get_groups_and_orders(args, grouper):
     # figure out orders and what the single group name would be if there were one
     single_group_name = []
     unique_cache = dict()
-    grp_to_idx = dict()
 
     for i, col in enumerate(grouper):
         if col == one_group:
@@ -2440,27 +2439,31 @@ def get_groups_and_orders(args, grouper):
             else:
                 orders[col] = list(OrderedDict.fromkeys(list(orders[col]) + uniques))
 
-    grp_to_idx = {k: i for i, k in enumerate(orders)}
-
     if len(single_group_name) == len(grouper):
         # we have a single group, so we can skip all group-by operations!
         groups = {tuple(single_group_name): df}
     else:
-        required_grouper = list(orders.keys())
+        required_grouper = [
+            key for key in orders if key in grouper and key != one_group
+        ]
+        order_mapping = {key: orders[key] for key in required_grouper}
         grouped = dict(df.group_by(required_grouper, drop_null_keys=True).__iter__())
-        sorted_group_names = list(grouped.keys())
 
-        for i, col in reversed(list(enumerate(required_grouper))):
-            sorted_group_names = sorted(
-                sorted_group_names,
-                key=lambda g: orders[col].index(g[i]) if g[i] in orders[col] else -1,
-            )
+        sorted_group_names = sorted(
+            grouped.keys(),
+            key=lambda group: [
+                order_mapping[key].index(value) if value in order_mapping[key] else -1
+                for key, value in zip(required_grouper, group)
+            ],
+        )
 
         # calculate the full group_names by inserting "" in the tuple index for one_group groups
         full_sorted_group_names = [
             tuple(
                 [
-                    "" if col == one_group else sub_group_names[grp_to_idx[col]]
+                    ""
+                    if col == one_group
+                    else sub_group_names[required_grouper.index(col)]
                     for col in grouper
                 ]
             )

Diff for: packages/python/plotly/plotly/tests/test_optional/test_px/test_px.py

@@ -289,6 +289,27 @@ def test_orthogonal_orderings(backend, days, times):
     assert_orderings(backend, days, days, times, times)
 
 
+def test_category_order_with_category_as_x(backend):
+    # https://github.com/plotly/plotly.py/issues/4875
+    tips = nw.from_native(px.data.tips(return_type=backend))
+    fig = px.bar(
+        tips,
+        x="day",
+        y="total_bill",
+        color="smoker",
+        barmode="group",
+        facet_col="sex",
+        category_orders={
+            "day": ["Thur", "Fri", "Sat", "Sun"],
+            "smoker": ["Yes", "No"],
+            "sex": ["Male", "Female"],
+        },
+    )
+    assert fig["layout"]["xaxis"]["categoryarray"] == ("Thur", "Fri", "Sat", "Sun")
+    for trace in fig["data"]:
+        assert sorted(set(trace["x"])) == ["Fri", "Sat", "Sun", "Thur"]
+
+
 def test_permissive_defaults():
     msg = "'PxDefaults' object has no attribute 'should_not_work'"
     with pytest.raises(AttributeError, match=msg):