Px special inputs

packages/python/plotly/plotly/express/__init__.py

@@ -53,6 +53,8 @@
     set_mapbox_access_token,
     defaults,
     get_trendline_results,
+    IdentityMap,
+    Constant,
 )
 
 from . import data, colors  # noqa: F401
@@ -95,4 +97,6 @@
     "colors",
     "set_mapbox_access_token",
     "get_trendline_results",
+    "IdentityMap",
+    "Constant",
 ]

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

@@ -41,6 +41,30 @@ def __init__(self):
 defaults = PxDefaults()
 del PxDefaults
 
+
+class IdentityMap(object):
+    """
+    `dict`-like object which can be passed in to arguments like `color_discrete_map` to
+    use the provided data values as colors, rather than mapping them to colors cycled
+    from `color_discrete_sequence`.
+    """
+
+    def __getitem__(self, key):
+        return key
+
+    def __contains__(self, key):
+        return True
+
+    def copy(self):
+        return self
+
+
+class Constant(object):
+    def __init__(self, value, label=None):
+        self.value = value
+        self.label = label
+
+
 MAPBOX_TOKEN = None
 
 
@@ -919,6 +943,8 @@ def build_dataframe(args, attrables, array_attrables):
         else:
             df_output[df_input.columns] = df_input[df_input.columns]
 
+    constants = dict()
+
     # Loop over possible arguments
     for field_name in attrables:
         # Massaging variables
@@ -950,8 +976,15 @@ def build_dataframe(args, attrables, array_attrables):
                     "pandas MultiIndex is not supported by plotly express "
                     "at the moment." % field
                 )
+            # ----------------- argument is a constant ----------------------
+            if isinstance(argument, Constant):
+                col_name = _check_name_not_reserved(
+                    str(argument.label) if argument.label is not None else field,
+                    reserved_names,
+                )
+                constants[col_name] = argument.value
             # ----------------- argument is a col name ----------------------
-            if isinstance(argument, str) or isinstance(
+            elif isinstance(argument, str) or isinstance(
                 argument, int
             ):  # just a column name given as str or int
                 if not df_provided:
@@ -1032,6 +1065,9 @@ def build_dataframe(args, attrables, array_attrables):
             else:
                 args[field_name][i] = str(col_name)
 
+    for col_name in constants:
+        df_output[col_name] = constants[col_name]
+
     args["data_frame"] = df_output
     return args
 
@@ -1402,9 +1438,10 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
         for col, val, m in zip(grouper, group_name, grouped_mappings):
             if col != one_group:
                 key = get_label(args, col)
-                mapping_labels[key] = str(val)
-                if m.show_in_trace_name:
-                    trace_name_labels[key] = str(val)
+                if not isinstance(m.val_map, IdentityMap):
+                    mapping_labels[key] = str(val)
+                    if m.show_in_trace_name:
+                        trace_name_labels[key] = str(val)
                 if m.variable == "animation_frame":
                     frame_name = val
         trace_name = ", ".join(trace_name_labels.values())

packages/python/plotly/plotly/tests/test_core/test_px/test_px_input.py

@@ -323,3 +323,48 @@ def test_size_column():
     df = px.data.tips()
     fig = px.scatter(df, x=df["size"], y=df.tip)
     assert fig.data[0].hovertemplate == "size=%{x}<br>tip=%{y}<extra></extra>"
+
+
+def test_identity_map():
+    fig = px.scatter(
+        x=[1, 2],
+        y=[1, 2],
+        symbol=["a", "b"],
+        color=["red", "blue"],
+        color_discrete_map=px.IdentityMap(),
+    )
+    assert fig.data[0].marker.color == "red"
+    assert fig.data[1].marker.color == "blue"
+    assert "color=" not in fig.data[0].hovertemplate
+    assert "symbol=" in fig.data[0].hovertemplate
+    assert fig.layout.legend.title.text == "symbol"
+
+
+def test_constants():
+    fig = px.scatter(x=px.Constant(1), y=[1, 2])
+    assert fig.data[0].x[0] == 1
+    assert fig.data[0].x[1] == 1
+    assert "x=" in fig.data[0].hovertemplate
+
+    fig = px.scatter(x=px.Constant(1, label="time"), y=[1, 2])
+    assert fig.data[0].x[0] == 1
+    assert fig.data[0].x[1] == 1
+    assert "x=" not in fig.data[0].hovertemplate
+    assert "time=" in fig.data[0].hovertemplate
+
+    fig = px.scatter(
+        x=[1, 2],
+        y=[1, 2],
+        symbol=["a", "b"],
+        color=px.Constant("red", label="the_identity_label"),
+        hover_data=[px.Constant("data", label="the_data")],
+        color_discrete_map=px.IdentityMap(),
+    )
+    assert fig.data[0].marker.color == "red"
+    assert fig.data[0].customdata[0][0] == "data"
+    assert fig.data[1].marker.color == "red"
+    assert "color=" not in fig.data[0].hovertemplate
+    assert "the_identity_label=" not in fig.data[0].hovertemplate
+    assert "symbol=" in fig.data[0].hovertemplate
+    assert "the_data=" in fig.data[0].hovertemplate
+    assert fig.layout.legend.title.text == "symbol"