Altair Styling & Themes

🌈 Color scales

alt.Color("category:N", scale=alt.Scale(scheme="category10"))
alt.Color("value:Q", scale=alt.Scale(scheme="viridis"))
alt.Color("value:Q", scale=alt.Scale(scheme="redblue", domainMid=0))    # diverging, centered
 
alt.Color("category:N", scale=alt.Scale(range=["#e74c3c", "#3498db", "#2ecc71"]))   # manual colors

Scheme category	Examples
Categorical	"category10", "category20", "tableau10"
Sequential	"blues", "viridis", "greens"
Diverging	"redblue", "purpleorange"

🏷️ Axis and legend customization

alt.X("value:Q", axis=alt.Axis(title="Total Value", format="$.2f", labelAngle=45))
alt.Color("category:N", legend=alt.Legend(title="Category", orient="bottom"))
alt.Y("value:Q", axis=None)      # hide the axis entirely

⚙️ Chart-level configure

chart.configure_axis(labelFontSize=12, titleFontSize=14, grid=False)
chart.configure_title(fontSize=18, anchor="start")
chart.configure_view(strokeWidth=0)          # remove the chart border
chart.configure_mark(opacity=0.8)

.configure_X() methods only work on the TOP-LEVEL chart (after composing with |, &, +) — calling them on a sub-chart before composition has no effect on the final output.

🎨 Built-in themes

alt.themes.enable("dark")
alt.themes.enable("fivethirtyeight")
alt.themes.enable("googlecharts")
print(alt.themes.names())      # list all available themes

alt.themes.enable("default")   # reset back to default

Enabling a theme is global — set once near the top of a script/notebook, every chart created after inherits it, same idea as sns.set_theme() in Seaborn.

🖌️ Custom theme

def my_theme():
    return {
        "config": {
            "view": {"strokeWidth": 0},
            "axis": {"grid": False},
            "range": {"category": ["#e74c3c", "#3498db", "#2ecc71"]}
        }
    }
 
alt.themes.register("my_theme", my_theme)
alt.themes.enable("my_theme")

📐 Sizing and shape

chart.properties(width=500, height=300)
chart.mark_point(size=100)
chart.properties(width="container")      # responsive — fills parent container width (in HTML embed contexts)

🔗 Next

Altair Saving & Exporting · Altair Composition & Layouts