categorical choropleths

packages/python/plotly/plotly/express/_chart_types.py

@@ -840,6 +840,8 @@ def choropleth(
     lon=None,
     locations=None,
     locationmode=None,
+    geojson=None,
+    featureidkey=None,
     color=None,
     hover_name=None,
     hover_data=None,
@@ -848,6 +850,8 @@ def choropleth(
     animation_group=None,
     category_orders={},
     labels={},
+    color_discrete_sequence=None,
+    color_discrete_map={},
     color_continuous_scale=None,
     range_color=None,
     color_continuous_midpoint=None,
@@ -866,7 +870,13 @@ def choropleth(
     return make_figure(
         args=locals(),
         constructor=go.Choropleth,
-        trace_patch=dict(locationmode=locationmode),
+        trace_patch=dict(
+            locationmode=locationmode,
+            featureidkey=featureidkey,
+            geojson=geojson
+            if not hasattr(geojson, "__geo_interface__")  # for geopandas
+            else geojson.__geo_interface__,
+        ),
     )
 
 
@@ -1003,6 +1013,7 @@ def scatter_mapbox(
 def choropleth_mapbox(
     data_frame=None,
     geojson=None,
+    featureidkey=None,
     locations=None,
     color=None,
     hover_name=None,
@@ -1012,6 +1023,8 @@ def choropleth_mapbox(
     animation_group=None,
     category_orders={},
     labels={},
+    color_discrete_sequence=None,
+    color_discrete_map={},
     color_continuous_scale=None,
     range_color=None,
     color_continuous_midpoint=None,
@@ -1032,9 +1045,10 @@ def choropleth_mapbox(
         args=locals(),
         constructor=go.Choroplethmapbox,
         trace_patch=dict(
+            featureidkey=featureidkey,
             geojson=geojson
-            if not hasattr(geojson, "__geo_interface__")
-            else geojson.__geo_interface__
+            if not hasattr(geojson, "__geo_interface__")  # for geopandas
+            else geojson.__geo_interface__,
         ),
     )
 

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

@@ -1250,8 +1250,9 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
                 if val not in m.val_map:
                     m.val_map[val] = m.sequence[len(m.val_map) % len(m.sequence)]
                 try:
-                    m.updater(trace, m.val_map[val])
+                    m.updater(trace, m.val_map[val])  # covers most cases
                 except ValueError:
+                    # this catches some odd cases like marginals
                     if (
                         trace_spec != trace_specs[0]
                         and trace_spec.constructor in [go.Violin, go.Box, go.Histogram]
@@ -1264,6 +1265,16 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
                         and m.variable == "color"
                     ):
                         trace.update(marker=dict(color=m.val_map[val]))
+                    elif (
+                        trace_spec.constructor in [go.Choropleth, go.Choroplethmapbox]
+                        and m.variable == "color"
+                    ):
+                        trace.update(
+                            z=[1] * len(group),
+                            colorscale=[m.val_map[val]] * 2,
+                            showscale=False,
+                            showlegend=True,
+                        )
                     else:
                         raise
 

packages/python/plotly/plotly/express/_doc.py

@@ -471,6 +471,11 @@
         "GeoJSON-formatted dict",
         "Must contain a Polygon feature collection, with IDs, which are references from `locations`.",
     ],
+    featureidkey=[
+        "str (default: `'id'`)",
+        "Path to field in GeoJSON feature object with which to match the values passed in to `locations`."
+        "The most common alternative to the default is of the form `'properties.<key>`.",
+    ],
     cumulative=[
         "boolean (default `False`)",
         "If `True`, histogram values are cumulative.",