feat(altair): implement bar-race-animated (#7323)

## Implementation: `bar-race-animated` - python/altair

Implements the **python/altair** version of `bar-race-animated`.

**File:** `plots/bar-race-animated/implementations/python/altair.py`

**Parent Issue:** #3653

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/26071184942)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: github-actions[bot]

plots/bar-race-animated/implementations/python/altair.py

@@ -1,14 +1,37 @@
-""" pyplots.ai
+""" anyplot.ai
 bar-race-animated: Animated Bar Chart Race
-Library: altair 6.0.0 | Python 3.13.11
-Quality: 91/100 | Created: 2026-01-11
+Library: altair 6.1.0 | Python 3.13.13
+Quality: 89/100 | Updated: 2026-05-19
 """
 
+import os
+
 import altair as alt
 import numpy as np
 import pandas as pd
 
 
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+
+# Okabe-Ito palette (first series always #009E73) + accessible extensions for 10 entities
+COLORS = [
+    "#009E73",  # Okabe-Ito pos 1 — brand green, always first
+    "#D55E00",  # Okabe-Ito pos 2 — vermillion
+    "#0072B2",  # Okabe-Ito pos 3 — blue
+    "#CC79A7",  # Okabe-Ito pos 4 — reddish purple
+    "#E69F00",  # Okabe-Ito pos 5 — orange
+    "#56B4E9",  # Okabe-Ito pos 6 — sky blue
+    "#F0E442",  # Okabe-Ito pos 7 — yellow
+    "#332288",  # accessible extension — deep indigo
+    "#117733",  # accessible extension — deep green
+    "#882255",  # accessible extension — deep crimson
+]
+
 # Data: Simulated streaming platform subscribers (millions) over time
 np.random.seed(42)
 
@@ -26,8 +49,6 @@
 ]
 years = list(range(2015, 2025))
 
-# Generate evolving subscriber counts with different growth trajectories
-data = []
 base_values = {
     "StreamFlix": 40,
     "ViewMax": 35,
@@ -53,6 +74,7 @@
     "CloudTV": 1.06,
 }
 
+data = []
 for platform in platforms:
     value = base_values[platform]
     for year in years:
@@ -65,25 +87,26 @@
 # Select key years for small multiples
 key_years = [2015, 2018, 2021, 2024]
 df_key = df[df["Year"].isin(key_years)].copy()
-
-# Add rank for each year (used for sorting within each facet)
 df_key["Rank"] = df_key.groupby("Year")["Subscribers"].rank(ascending=True, method="first").astype(int)
 
-# Color palette with Python Blue and Yellow first
-colors = ["#306998", "#FFD43B", "#4A90D9", "#2ECC71", "#E74C3C", "#9B59B6", "#F39C12", "#1ABC9C", "#34495E", "#E67E22"]
-
-# Create single bar chart that will be faceted
+# Bar chart layer
 bar_chart = (
     alt.Chart(df_key)
     .mark_bar(cornerRadiusEnd=6, height=45)
     .encode(
         x=alt.X(
             "Subscribers:Q",
             title="Subscribers (millions)",
-            axis=alt.Axis(labelFontSize=16, titleFontSize=20, grid=True, gridOpacity=0.3),
+            axis=alt.Axis(labelFontSize=16, titleFontSize=20, grid=True, gridOpacity=0.25),
         ),
         y=alt.Y("Rank:O", title=None, axis=None, sort="descending"),
-        color=alt.Color("Platform:N", scale=alt.Scale(domain=platforms, range=colors), legend=None),
+        color=alt.Color(
+            "Platform:N",
+            scale=alt.Scale(domain=platforms, range=COLORS),
+            legend=alt.Legend(
+                title="Platform", labelFontSize=16, titleFontSize=18, symbolSize=160, padding=14, cornerRadius=4
+            ),
+        ),
         tooltip=[
             alt.Tooltip("Platform:N", title="Platform"),
             alt.Tooltip("Subscribers:Q", format=".1f", title="Subscribers (M)"),
@@ -92,22 +115,22 @@
     )
 )
 
-# Add text labels on bars
+# Platform name labels outside bars
 text_labels = (
     alt.Chart(df_key)
     .mark_text(align="left", dx=8, fontSize=14, fontWeight="bold")
     .encode(
         x=alt.X("Subscribers:Q"),
         y=alt.Y("Rank:O", sort="descending"),
         text=alt.Text("Platform:N"),
-        color=alt.value("#333333"),
+        color=alt.value(INK),
     )
 )
 
-# Value labels at end of bars
+# Value labels inside bars
 value_labels = (
     alt.Chart(df_key)
-    .mark_text(align="right", dx=-8, fontSize=13, fontWeight="normal")
+    .mark_text(align="right", dx=-8, fontSize=16, fontWeight="normal")
     .encode(
         x=alt.X("Subscribers:Q"),
         y=alt.Y("Rank:O", sort="descending"),
@@ -116,29 +139,41 @@
     )
 )
 
-# Combine layers - target 4800x2700 at scale 3x = 1600x900 base
+# Combine layers and facet by year
 combined = (bar_chart + text_labels + value_labels).properties(width=340, height=750)
 
-# Facet by year
 chart = (
     combined.facet(
-        column=alt.Column("Year:O", header=alt.Header(labelFontSize=26, title=None, labelPadding=15)), spacing=20
+        column=alt.Column("Year:O", header=alt.Header(labelFontSize=26, title=None, labelPadding=15, labelColor=INK)),
+        spacing=20,
     )
-    .configure_view(strokeWidth=0)
-    .configure_axis(labelFontSize=18, titleFontSize=22)
     .properties(
         title=alt.Title(
-            "bar-race-animated · altair · pyplots.ai",
+            "bar-race-animated · python · altair · anyplot.ai",
             fontSize=34,
             anchor="middle",
             subtitle="Streaming Platform Subscribers Over Time (millions)",
             subtitleFontSize=22,
             dy=-10,
-        )
+        ),
+        background=PAGE_BG,
+    )
+    .configure_view(strokeWidth=0, fill=PAGE_BG)
+    .configure_axis(
+        labelFontSize=18,
+        titleFontSize=22,
+        domainColor=INK_SOFT,
+        tickColor=INK_SOFT,
+        gridColor=INK_SOFT,
+        gridOpacity=0.20,
+        labelColor=INK_SOFT,
+        titleColor=INK,
     )
+    .configure_title(color=INK, subtitleColor=INK_SOFT)
+    .configure_legend(fillColor=ELEVATED_BG, strokeColor=INK_SOFT, labelColor=INK_SOFT, titleColor=INK)
     .resolve_scale(x="independent")
 )
 
-# Save outputs
-chart.save("plot.png", scale_factor=3.0)
-chart.save("plot.html")
+# Save
+chart.save(f"plot-{THEME}.png", scale_factor=3.0)
+chart.save(f"plot-{THEME}.html")