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Author: nicolaskruchten

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

@@ -53,6 +53,9 @@
     set_mapbox_access_token,
     defaults,
     get_trendline_results,
+)
+
+from ._special_inputs import (  # noqa: F401
     IdentityMap,
     Constant,
 )

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

@@ -1,6 +1,7 @@
 import plotly.graph_objs as go
 import plotly.io as pio
 from collections import namedtuple, OrderedDict
+from ._special_inputs import IdentityMap, Constant
 
 from _plotly_utils.basevalidators import ColorscaleValidator
 from .colors import qualitative, sequential
@@ -42,29 +43,6 @@ def __init__(self):
 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
 
 
@@ -161,11 +139,15 @@ def make_mapping(args, variable):
     if variable == "dash":
         arg_name = "line_dash"
         vprefix = "line_dash"
+    if args[vprefix + "_map"] == "identity":
+        val_map = IdentityMap()
+    else:
+        val_map = args[vprefix + "_map"].copy()
     return Mapping(
         show_in_trace_name=True,
         variable=variable,
         grouper=args[arg_name],
-        val_map=args[vprefix + "_map"].copy(),
+        val_map=val_map,
         sequence=args[vprefix + "_sequence"],
         updater=lambda trace, v: trace.update({parent: {variable: v}}),
         facet=None,

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

@@ -0,0 +1,29 @@
+
+class IdentityMap(object):
+    """
+    `dict`-like object which acts as if the value for any key is the key itself. Objects
+    of this class 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`. This works for any `_map` argument to Plotly Express
+    functions, such as `line_dash_map` and `symbol_map`.
+    """
+
+    def __getitem__(self, key):
+        return key
+
+    def __contains__(self, key):
+        return True
+
+    def copy(self):
+        return self
+
+
+class Constant(object):
+    """
+    Objects of this class can be passed to Plotly Express functions that expect column
+    identifiers or list-like objects to indicate that this attribute should take on a
+    constant value. An optional label can be provided.
+    """
+    def __init__(self, value, label=None):
+        self.value = value
+        self.label = label

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

@@ -339,6 +339,19 @@ def test_identity_map():
     assert "symbol=" in fig.data[0].hovertemplate
     assert fig.layout.legend.title.text == "symbol"
 
+    fig = px.scatter(
+        x=[1, 2],
+        y=[1, 2],
+        symbol=["a", "b"],
+        color=["red", "blue"],
+        color_discrete_map="identity",
+    )
+    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])