px.NO_COLOR

Author: nicolaskruchten

Diff for: CHANGELOG.md

@@ -2,6 +2,13 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [4.9.0] - unreleased
+
+### Added
+
+- `px.NO_COLOR` constant to override wide-form color assignment
+
+
 ## [4.8.2] - 2020-06-26
 
 ### Updated

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

@@ -53,6 +53,7 @@
     set_mapbox_access_token,
     defaults,
     get_trendline_results,
+    NO_COLOR,
 )
 
 from ._special_inputs import IdentityMap, Constant, Range  # noqa: F401
@@ -100,4 +101,5 @@
     "IdentityMap",
     "Constant",
     "Range",
+    "NO_COLOR",
 ]

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

@@ -15,6 +15,7 @@
     _subplot_type_for_trace_type,
 )
 
+NO_COLOR = "px_no_color_constant"
 
 # Declare all supported attributes, across all plot types
 direct_attrables = (
@@ -1349,6 +1350,10 @@ def build_dataframe(args, constructor):
                     label=_escape_col_name(df_input, "index", [var_name, value_name])
                 )
 
+    no_color = False
+    if args.get("color", None) == NO_COLOR:
+        no_color = True
+        args["color"] = None
     # now that things have been prepped, we do the systematic rewriting of `args`
 
     df_output, wide_id_vars = process_args_into_dataframe(
@@ -1440,7 +1445,8 @@ def build_dataframe(args, constructor):
             args["x" if orient_v else "y"] = value_name
             args["y" if orient_v else "x"] = wide_cross_name
             args["color"] = args["color"] or var_name
-
+    if no_color:
+        args["color"] = None
     args["data_frame"] = df_output
     return args
 

Diff for: packages/python/plotly/plotly/tests/test_core/test_px/test_px_wide.py

@@ -708,6 +708,17 @@ def append_special_case(df_in, args_in, args_expect, df_expect):
     ),
 )
 
+# NO_COLOR
+df = pd.DataFrame(dict(a=[1, 2], b=[3, 4]))
+append_special_case(
+    df_in=df,
+    args_in=dict(x=None, y=None, color=px.NO_COLOR),
+    args_expect=dict(x="index", y="value", color=None, orientation="v",),
+    df_expect=pd.DataFrame(
+        dict(variable=["a", "a", "b", "b"], index=[0, 1, 0, 1], value=[1, 2, 3, 4])
+    ),
+)
+
 
 @pytest.mark.parametrize("df_in, args_in, args_expect, df_expect", special_cases)
 def test_wide_mode_internal_special_cases(df_in, args_in, args_expect, df_expect):