From 8ed1ecc4748a4aae52f7dfb8e25fa169a7a53f41 Mon Sep 17 00:00:00 2001
From: Emmanuelle Gouillart <emma@plot.ly>
Date: Fri, 5 Jun 2020 21:52:48 +0200
Subject: [PATCH 1/2] fixed bug in hover data

---
 packages/python/plotly/plotly/express/_core.py  | 17 +++++++++++++----
 .../tests/test_core/test_px/test_px_hover.py    | 12 ++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/packages/python/plotly/plotly/express/_core.py b/packages/python/plotly/plotly/express/_core.py
index df600555b14..30690abca5c 100644
--- a/packages/python/plotly/plotly/express/_core.py
+++ b/packages/python/plotly/plotly/express/_core.py
@@ -116,6 +116,14 @@ def get_label(args, column):
         return column
 
 
+def invert_label(args, column):
+    reversed_labels = {value: key for (key, value) in args["labels"].items()}
+    try:
+        return reversed_labels[column]
+    except Exception:
+        return column
+
+
 def _is_continuous(df, col_name):
     return df[col_name].dtype.kind in "ifc"
 
@@ -434,11 +442,12 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
         mapping_labels_copy = OrderedDict(mapping_labels)
         if args["hover_data"] and isinstance(args["hover_data"], dict):
             for k, v in mapping_labels.items():
-                if k in args["hover_data"]:
-                    if args["hover_data"][k][0]:
-                        if isinstance(args["hover_data"][k][0], str):
+                k_args = invert_label(args, k)
+                if k_args in args["hover_data"]:
+                    if args["hover_data"][k_args][0]:
+                        if isinstance(args["hover_data"][k_args][0], str):
                             mapping_labels_copy[k] = v.replace(
-                                "}", "%s}" % args["hover_data"][k][0]
+                                "}", "%s}" % args["hover_data"][k_args][0]
                             )
                     else:
                         _ = mapping_labels_copy.pop(k)
diff --git a/packages/python/plotly/plotly/tests/test_core/test_px/test_px_hover.py b/packages/python/plotly/plotly/tests/test_core/test_px/test_px_hover.py
index f63696e8dee..07d0e201a43 100644
--- a/packages/python/plotly/plotly/tests/test_core/test_px/test_px_hover.py
+++ b/packages/python/plotly/plotly/tests/test_core/test_px/test_px_hover.py
@@ -72,6 +72,18 @@ def test_newdatain_hover_data():
         )
 
 
+def test_formatted_hover_and_labels():
+    df = px.data.tips()
+    fig = px.scatter(
+        df,
+        x="tip",
+        y="total_bill",
+        hover_data={"total_bill": ":.1f"},
+        labels={"total_bill": "Total bill"},
+    )
+    assert ":.1f" in fig.data[0].hovertemplate
+
+
 def test_fail_wrong_column():
     with pytest.raises(ValueError) as err_msg:
         px.scatter(

From 23ef3b8f54415a27e57dd0baed89bf9fac513638 Mon Sep 17 00:00:00 2001
From: Emmanuelle Gouillart <emma@plot.ly>
Date: Fri, 12 Jun 2020 16:29:14 +0200
Subject: [PATCH 2/2] addressed review comments

---
 CHANGELOG.md                                   | 1 +
 packages/python/plotly/plotly/express/_core.py | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 985f3c231d0..5aca477f453 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fixed special cases with `px.sunburst` and `px.treemap` with `path` input ([#2524](https://github.com/plotly/plotly.py/pull/2524))
+- Fixed bug in `hover_data` argument of `px` functions, when the column name is changed with labels and `hover_data` is a dictionary setting up a specific format for the hover data ([#2544](https://github.com/plotly/plotly.py/pull/2544)).
 
 ## [4.8.1] - 2020-05-28
 
diff --git a/packages/python/plotly/plotly/express/_core.py b/packages/python/plotly/plotly/express/_core.py
index 30690abca5c..5d6388ae59d 100644
--- a/packages/python/plotly/plotly/express/_core.py
+++ b/packages/python/plotly/plotly/express/_core.py
@@ -117,6 +117,10 @@ def get_label(args, column):
 
 
 def invert_label(args, column):
+    """Invert mapping.
+    Find key corresponding to value column in dict args["labels"].
+    Returns `column` if the value does not exist.
+    """
     reversed_labels = {value: key for (key, value) in args["labels"].items()}
     try:
         return reversed_labels[column]
@@ -442,6 +446,7 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
         mapping_labels_copy = OrderedDict(mapping_labels)
         if args["hover_data"] and isinstance(args["hover_data"], dict):
             for k, v in mapping_labels.items():
+                # We need to invert the mapping here
                 k_args = invert_label(args, k)
                 if k_args in args["hover_data"]:
                     if args["hover_data"][k_args][0]: