Opacity feature

plotly_express/_chart_types.py

@@ -18,6 +18,7 @@ def scatter(
     x=None,
     y=None,
     color=None,
+    opacity=None,
     symbol=None,
     size=None,
     hover_name=None,
@@ -325,6 +326,7 @@ def scatter_3d(
     y=None,
     z=None,
     color=None,
+    opacity=None,
     symbol=None,
     size=None,
     text=None,
@@ -416,6 +418,7 @@ def scatter_ternary(
     b=None,
     c=None,
     color=None,
+    opacity=None,
     symbol=None,
     size=None,
     text=None,
@@ -483,6 +486,7 @@ def scatter_polar(
     r=None,
     theta=None,
     color=None,
+    opacity=None,
     symbol=None,
     size=None,
     hover_name=None,
@@ -774,6 +778,7 @@ def scatter_matrix(
     data_frame,
     dimensions=None,
     color=None,
+    opacity=None,
     symbol=None,
     size=None,
     category_orders={},

plotly_express/_core.py

@@ -133,6 +133,8 @@ def make_trace_kwargs(args, trace_spec, g, mapping_labels, sizeref, color_range)
                     or len(args["data_frame"][name].unique()) <= 20
                 )
             ]
+        elif k == 'opacity':
+            pass
         elif v or (trace_spec.constructor == go.Histogram and k in ["x", "y"]):
             if k == "size":
                 if "marker" not in result:
@@ -141,7 +143,6 @@ def make_trace_kwargs(args, trace_spec, g, mapping_labels, sizeref, color_range)
                 result["marker"]["sizemode"] = "area"
                 result["marker"]["sizeref"] = sizeref
                 mapping_labels.append(("%s=%%{%s}" % (v_label, "marker.size"), None))
-
             elif k == "trendline":
                 if v in ["ols", "lowess"] and args["x"] and args["y"] and len(g) > 1:
                     import statsmodels.api as sm
@@ -568,7 +569,7 @@ def one_group(x):
 
 def infer_config(args, constructor, trace_patch):
     attrables = (
-        ["x", "y", "z", "a", "b", "c", "r", "theta", "size"]
+        ["x", "y", "z", "a", "b", "c", "r", "theta", "size", "opacity"]
         + ["dimensions", "hover_name", "text", "error_x", "error_x_minus"]
         + ["error_y", "error_y_minus", "error_z", "error_z_minus"]
         + ["lat", "lon", "locations", "animation_group"]
@@ -620,6 +621,8 @@ def infer_config(args, constructor, trace_patch):
         grouped_attrs.append("marker.symbol")
 
     trace_patch = trace_patch.copy()
+    if "opacity" in args:
+        trace_patch["marker"] = dict(opacity=args["opacity"])
     if "line_group" in args:
         trace_patch["mode"] = "lines" + ("+markers+text" if args["text"] else "")
     elif constructor != go.Splom and (

plotly_express/_doc.py

@@ -91,6 +91,11 @@
         "Ignored if `error_z` is `None`.",
     ],
     color=[colref, "Values from this column are used to assign color to marks."],
+    opacity=[
+        colref,
+        "Sets the opacity of the markers in scatter plots such as `scatter()`",
+        ",`scatter_3d`, `scatter_ternary()`, `scatter_matrix()` and `scatter_polar()`."
+    ],
     line_dash=[
         colref,
         "Values from this column are used to assign dash-patterns to lines.",