fix groupby ordering when multi-grouping, should address #23

plotly_express/_core.py

@@ -756,24 +756,27 @@ def infer_config(args, constructor, trace_patch):
     return trace_specs, grouped_mappings, sizeref, color_range
 
 
-def make_figure(args, constructor, trace_patch={}, layout_patch={}):
-    apply_default_cascade(args)
-    trace_specs, grouped_mappings, sizeref, color_range = infer_config(
-        args, constructor, trace_patch
-    )
-    grouper = [x.grouper or one_group for x in grouped_mappings] or [one_group]
-    grouped = args["data_frame"].groupby(grouper, sort=False)
+def get_orderings(args, grouper, grouped):
+    """
+    `orders` is the user-supplied ordering (with the remaining data-frame-supplied
+    ordering appended if the column is used for grouping)
+    `group_names` is the set of groups, ordered by the order above
+    """
     orders = {} if "category_orders" not in args else args["category_orders"].copy()
     group_names = []
     for group_name in grouped.groups:
         if len(grouper) == 1:
             group_name = (group_name,)
         group_names.append(group_name)
-        for col, val in zip(grouper, group_name):
-            if col not in orders:
-                orders[col] = []
-            if val not in orders[col]:
-                orders[col].append(val)
+        for col in grouper:
+            if col != one_group:
+                uniques = args["data_frame"][col].unique()
+                if col not in orders:
+                    orders[col] = list(uniques)
+                else:
+                    for val in uniques:
+                        if val not in orders[col]:
+                            orders[col].append(val)
 
     for i, col in reversed(list(enumerate(grouper))):
         if col != one_group:
@@ -782,10 +785,23 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
                 key=lambda g: orders[col].index(g[i]) if g[i] in orders[col] else -1,
             )
 
+    return orders, group_names
+
+
+def make_figure(args, constructor, trace_patch={}, layout_patch={}):
+    apply_default_cascade(args)
+    trace_specs, grouped_mappings, sizeref, color_range = infer_config(
+        args, constructor, trace_patch
+    )
+    grouper = [x.grouper or one_group for x in grouped_mappings] or [one_group]
+    grouped = args["data_frame"].groupby(grouper, sort=False)
+
+    orders, sorted_group_names = get_orderings(args, grouper, grouped)
+
     trace_names_by_frame = {}
     frames = OrderedDict()
     trendline_rows = []
-    for group_name in group_names:
+    for group_name in sorted_group_names:
         group = grouped.get_group(group_name if len(group_name) > 1 else group_name[0])
         mapping_labels = OrderedDict()
         trace_name_labels = OrderedDict()