Top-Level Chart Configuration

Many aspects of a chart’s appearance can be configured at the top level using the configure_*() methods. These methods and the properties that they set are only valid at the top level of a chart, and can be thought of as a way of setting a chart theme: that is, they set the default styles for the entire chart, and these defaults can be overridden by specific style settings associated with chart elements.

These methods and their arguments will be outlined below:

• Chart Configuration Chart.configure()

• Axis Configuration Chart.configure_axis()

• Header Configuration Chart.configure_header()

• Legend Configuration Chart.configure_legend()

• Mark and Mark Style Configuration Chart.configure_mark()

• Scale Configuration Chart.configure_scale()

• Scale Range Configuration Chart.configure_range()

• Projection Configuration Chart.configure_projection()

• Selection Configuration Chart.configure_selection()

• Title Configuration Chart.configure_title()

• View Configuration Chart.configure_view()

For more discussion of approaches to chart customization, see Customizing Visualizations.

Chart Configuration

The Chart.configure() method adds a Config instance to the chart, and has the following attributes:

Property	Type	Description
arc	RectConfig	Arc-specific Config
area	AreaConfig	Area-Specific Config
aria	boolean	A boolean flag indicating if ARIA default attributes should be included for marks and guides (SVG output only). If false, the "aria-hidden" attribute will be set for all guides, removing them from the ARIA accessibility tree and Vega-Lite will not generate default descriptions for marks. Default value: true.
autosize	anyOf(AutosizeType, AutoSizeParams)	How the visualization size should be determined. If a string, should be one of "pad", "fit" or "none". Object values can additionally specify parameters for content sizing and automatic resizing. Default value: pad
axis	AxisConfig	Axis configuration, which determines default properties for all x and y axes. For a full list of axis configuration options, please see the corresponding section of the axis documentation.
axisBand	AxisConfig	Config for axes with “band” scales.
axisBottom	AxisConfig	Config for x-axis along the bottom edge of the chart.
axisDiscrete	AxisConfig	Config for axes with “point” or “band” scales.
axisLeft	AxisConfig	Config for y-axis along the left edge of the chart.
axisPoint	AxisConfig	Config for axes with “point” scales.
axisQuantitative	AxisConfig	Config for quantitative axes.
axisRight	AxisConfig	Config for y-axis along the right edge of the chart.
axisTemporal	AxisConfig	Config for temporal axes.
axisTop	AxisConfig	Config for x-axis along the top edge of the chart.
axisX	AxisConfig	X-axis specific config.
axisXBand	AxisConfig	Config for x-axes with “band” scales.
axisXDiscrete	AxisConfig	Config for x-axes with “point” or “band” scales.
axisXPoint	AxisConfig	Config for x-axes with “point” scales.
axisXQuantitative	AxisConfig	Config for x-quantitative axes.
axisXTemporal	AxisConfig	Config for x-temporal axes.
axisY	AxisConfig	Y-axis specific config.
axisYBand	AxisConfig	Config for y-axes with “band” scales.
axisYDiscrete	AxisConfig	Config for y-axes with “point” or “band” scales.
axisYPoint	AxisConfig	Config for y-axes with “point” scales.
axisYQuantitative	AxisConfig	Config for y-quantitative axes.
axisYTemporal	AxisConfig	Config for y-temporal axes.
background	anyOf(Color, ExprRef)	CSS color property to use as the background of the entire view. Default value: "white"
bar	BarConfig	Bar-Specific Config
boxplot	BoxPlotConfig	Box Config
circle	MarkConfig	Circle-Specific Config
concat	CompositionConfig	Default configuration for all concatenation and repeat view composition operators (concat, hconcat, vconcat, and repeat)
countTitle	string	Default axis and legend title for count fields. Default value: 'Count of Records.
customFormatTypes	boolean	Allow the formatType property for text marks and guides to accept a custom formatter function registered as a Vega expression.
errorband	ErrorBandConfig	ErrorBand Config
errorbar	ErrorBarConfig	ErrorBar Config
facet	CompositionConfig	Default configuration for the facet view composition operator
fieldTitle	[‘verbal’, ‘functional’, ‘plain’]	Defines how Vega-Lite generates title for fields. There are three possible styles: - "verbal" (Default) - displays function in a verbal style (e.g., “Sum of field”, “Year-month of date”, “field (binned)”). - "function" - displays function using parentheses and capitalized texts (e.g., “SUM(field)”, “YEARMONTH(date)”, “BIN(field)”). - "plain" - displays only the field name without functions (e.g., “field”, “date”, “field”).
font	string	Default font for all text marks, titles, and labels.
geoshape	MarkConfig	Geoshape-Specific Config
header	HeaderConfig	Header configuration, which determines default properties for all headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerColumn	HeaderConfig	Header configuration, which determines default properties for column headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerFacet	HeaderConfig	Header configuration, which determines default properties for non-row/column facet headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerRow	HeaderConfig	Header configuration, which determines default properties for row headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
image	RectConfig	Image-specific Config
legend	LegendConfig	Legend configuration, which determines default properties for all legends. For a full list of legend configuration options, please see the corresponding section of in the legend documentation.
line	LineConfig	Line-Specific Config
lineBreak	anyOf(string, ExprRef)	A delimiter, such as a newline character, upon which to break text strings into multiple lines. This property provides a global default for text marks, which is overridden by mark or style config settings, and by the lineBreak mark encoding channel. If signal-valued, either string or regular expression (regexp) values are valid.
mark	MarkConfig	Mark Config
numberFormat	string	D3 Number format for guide labels and text marks. For example "s" for SI units. Use D3’s number format pattern.
padding	anyOf(Padding, ExprRef)	The default visualization padding, in pixels, from the edge of the visualization canvas to the data rectangle. If a number, specifies padding for all sides. If an object, the value should have the format {"left": 5, "top": 5, "right": 5, "bottom": 5} to specify padding for each side of the visualization. Default value: 5
params	array(Parameter)	Dynamic variables that parameterize a visualization.
point	MarkConfig	Point-Specific Config
projection	ProjectionConfig	Projection configuration, which determines default properties for all projections. For a full list of projection configuration options, please see the corresponding section of the projection documentation.
range	RangeConfig	An object hash that defines default range arrays or schemes for using with scales. For a full list of scale range configuration options, please see the corresponding section of the scale documentation.
rect	RectConfig	Rect-Specific Config
rule	MarkConfig	Rule-Specific Config
scale	ScaleConfig	Scale configuration determines default properties for all scales. For a full list of scale configuration options, please see the corresponding section of the scale documentation.
selection	SelectionConfig	An object hash for defining default properties for each type of selections.
square	MarkConfig	Square-Specific Config
style	StyleConfigIndex	An object hash that defines key-value mappings to determine default properties for marks with a given style. The keys represent styles names; the values have to be valid mark configuration objects.
text	MarkConfig	Text-Specific Config
tick	TickConfig	Tick-Specific Config
timeFormat	string	Default time format for raw time values (without time units) in text marks, legend labels and header labels. Default value: "%b %d, %Y" Note: Axes automatically determine the format for each label automatically so this config does not affect axes.
title	TitleConfig	Title configuration, which determines default properties for all titles. For a full list of title configuration options, please see the corresponding section of the title documentation.
trail	LineConfig	Trail-Specific Config
view	ViewConfig	Default properties for single view plots.

Axis Configuration

Axis configuration defines default settings for axes, and can be set using the Chart.configure_axis() method. Properties defined here are applied to all axes in the figure.

Additional property blocks can target more specific axis types based on the orientation (“axisX”, “axisY”, “axisLeft”, “axisTop”, etc.) or band scale type (“axisBand”). For example, properties defined under the “axisBand” property will only apply to axes visualizing “band” scales. If multiple axis config blocks apply to a single axis, type-based options take precedence over orientation-based options, which in turn take precedence over general options.

The methods are the following:

• Chart.configure_axis()

• Chart.configure_axisBand()

• Chart.configure_axisBottom()

• Chart.configure_axisLeft()

• Chart.configure_axisRight()

• Chart.configure_axisTop()

• Chart.configure_axisX()

• Chart.configure_axisY()

They have the following properties:

Property	Type	Description
aria	anyOf(boolean, ExprRef)
bandPosition	anyOf(number, ExprRef)
description	anyOf(string, ExprRef)
disable	boolean	Disable axis by default.
domain	anyOf(boolean, ExprRef)
domainCap	anyOf(StrokeCap, ExprRef)
domainColor	anyOf(anyOf(null, Color), ExprRef)
domainDash	anyOf(array(number), ExprRef)
domainDashOffset	anyOf(number, ExprRef)
domainOpacity	anyOf(number, ExprRef)
domainWidth	anyOf(number, ExprRef)
format	anyOf(string, Dict<unknown>)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. - If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: - "time" for temporal fields and ordinal and nominal fields with timeUnit. - "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
grid	boolean	A boolean flag indicating if grid lines should be included as part of the axis Default value: true for continuous scales that are not binned; otherwise, false.
gridCap	anyOf(StrokeCap, ExprRef)
gridColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)
gridDash	anyOf(array(number), ExprRef, ConditionalAxisNumberArray)
gridDashOffset	anyOf(number, ExprRef, ConditionalAxisNumber)
gridOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)
gridWidth	anyOf(number, ExprRef, ConditionalAxisNumber)
labelAlign	anyOf(Align, ExprRef, ConditionalAxisLabelAlign)
labelAngle	anyOf(number, ExprRef)
labelBaseline	anyOf(TextBaseline, ExprRef, ConditionalAxisLabelBaseline)
labelBound	anyOf([number, boolean], ExprRef)
labelColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)
labelExpr	string	Vega expression for customizing labels text. Note: The label text and value can be assessed via the label and value properties of the axis’s backing datum object.
labelFlush	[boolean, number]	Indicates if the first and last axis labels should be aligned flush with the scale range. Flush alignment for a horizontal axis will left-align the first label and right-align the last label. For vertical axes, bottom and top text baselines are applied instead. If this property is a number, it also indicates the number of pixels by which to offset the first and last labels; for example, a value of 2 will flush-align the first and last labels and also push them 2 pixels outward from the center of the axis. The additional adjustment can sometimes help the labels better visually group with corresponding axis ticks. Default value: true for axis of a continuous x-scale. Otherwise, false.
labelFlushOffset	anyOf(number, ExprRef)
labelFont	anyOf(string, ExprRef, ConditionalAxisString)
labelFontSize	anyOf(number, ExprRef, ConditionalAxisNumber)
labelFontStyle	anyOf(FontStyle, ExprRef, ConditionalAxisLabelFontStyle)
labelFontWeight	anyOf(FontWeight, ExprRef, ConditionalAxisLabelFontWeight)
labelLimit	anyOf(number, ExprRef)
labelLineHeight	anyOf(number, ExprRef)
labelOffset	anyOf(number, ExprRef, ConditionalAxisNumber)
labelOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)
labelOverlap	anyOf(LabelOverlap, ExprRef)	The strategy to use for resolving overlap of axis labels. If false (the default), no overlap reduction is attempted. If set to true or "parity", a strategy of removing every other label is used (this works well for standard linear axes). If set to "greedy", a linear scan of the labels is performed, removing any labels that overlaps with the last visible label (this often works better for log-scaled axes). Default value: true for non-nominal fields with non-log scales; "greedy" for log scales; otherwise false.
labelPadding	anyOf(number, ExprRef, ConditionalAxisNumber)
labelSeparation	anyOf(number, ExprRef)
labels	anyOf(boolean, ExprRef)
maxExtent	anyOf(number, ExprRef)
minExtent	anyOf(number, ExprRef)
offset	number	The offset, in pixels, by which to displace the axis from the edge of the enclosing group or data rectangle. Default value: derived from the axis config’s offset (0 by default)
orient	anyOf(AxisOrient, ExprRef)	The orientation of the axis. One of "top", "bottom", "left" or "right". The orientation can be used to further specialize the axis type (e.g., a y-axis oriented towards the right edge of the chart). Default value: "bottom" for x-axes and "left" for y-axes.
position	anyOf(number, ExprRef)	The anchor position of the axis in pixels. For x-axes with top or bottom orientation, this sets the axis group x coordinate. For y-axes with left or right orientation, this sets the axis group y coordinate. Default value: 0
style	anyOf(string, array(string))	A string or array of strings indicating the name of custom styles to apply to the axis. A style is a named collection of axis property defined within the style configuration. If style is an array, later styles will override earlier styles. Default value: (none) Note: Any specified style will augment the default style. For example, an x-axis mark with "style": "foo" will use config.axisX and config.style.foo (the specified style "foo" has higher precedence).
tickBand	anyOf([‘center’, ‘extent’], ExprRef)
tickCap	anyOf(StrokeCap, ExprRef)
tickColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)
tickCount	anyOf(number, TimeInterval, TimeIntervalStep, ExprRef)	A desired number of ticks, for axes visualizing quantitative scales. The resulting number may be different so that values are “nice” (multiples of 2, 5, 10) and lie within the underlying scale’s range. For scales of type "time" or "utc", the tick count can instead be a time interval specifier. Legal string values are "millisecond", "second", "minute", "hour", "day", "week", "month", and "year". Alternatively, an object-valued interval specifier of the form {"interval": "month", "step": 3} includes a desired number of interval steps. Here, ticks are generated for each quarter (Jan, Apr, Jul, Oct) boundary. Default value: Determine using a formula ceil(width/40) for x and ceil(height/40) for y.
tickDash	anyOf(array(number), ExprRef, ConditionalAxisNumberArray)
tickDashOffset	anyOf(number, ExprRef, ConditionalAxisNumber)
tickExtra	anyOf(boolean, ExprRef)
tickMinStep	anyOf(number, ExprRef)	The minimum desired step between axis ticks, in terms of scale domain values. For example, a value of 1 indicates that ticks should not be less than 1 unit apart. If tickMinStep is specified, the tickCount value will be adjusted, if necessary, to enforce the minimum step value.
tickOffset	anyOf(number, ExprRef)
tickOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)
tickRound	anyOf(boolean, ExprRef)
tickSize	anyOf(number, ExprRef, ConditionalAxisNumber)
tickWidth	anyOf(number, ExprRef, ConditionalAxisNumber)
ticks	anyOf(boolean, ExprRef)
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
titleAlign	anyOf(Align, ExprRef)
titleAnchor	anyOf(TitleAnchor, ExprRef)
titleAngle	anyOf(number, ExprRef)
titleBaseline	anyOf(TextBaseline, ExprRef)
titleColor	anyOf(anyOf(null, Color), ExprRef)
titleFont	anyOf(string, ExprRef)
titleFontSize	anyOf(number, ExprRef)
titleFontStyle	anyOf(FontStyle, ExprRef)
titleFontWeight	anyOf(FontWeight, ExprRef)
titleLimit	anyOf(number, ExprRef)
titleLineHeight	anyOf(number, ExprRef)
titleOpacity	anyOf(number, ExprRef)
titlePadding	anyOf(number, ExprRef)
titleX	anyOf(number, ExprRef)
titleY	anyOf(number, ExprRef)
translate	anyOf(number, ExprRef)
values	anyOf(array(number), array(string), array(boolean), array(DateTime), ExprRef)	Explicitly set the visible axis tick values.
zindex	number	A non-negative integer indicating the z-index of the axis. If zindex is 0, axes should be drawn behind all chart elements. To put them in front, set zindex to 1 or more. Default value: 0 (behind the marks).

Header Configuration

The Chart.configure_header() method allows configuration of facet headers, including the font, color, size, and position of the title and labels. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
    color='Origin:N',
    column='Origin:N'
).properties(
    width=180,
    height=180
)

chart.configure_header(
    titleColor='green',
    titleFontSize=14,
    labelColor='red',
    labelFontSize=14
)

Property	Type	Description
format	anyOf(string, Dict<unknown>)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. - If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: - "time" for temporal fields and ordinal and nominal fields with timeUnit. - "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
labelAlign	anyOf(Align, ExprRef)	Horizontal text alignment of header labels. One of "left", "center", or "right".
labelAnchor	TitleAnchor	The anchor position for placing the labels. One of "start", "middle", or "end". For example, with a label orientation of top these anchor positions map to a left-, center-, or right-aligned label.
labelAngle	number	The rotation angle of the header labels. Default value: 0 for column header, -90 for row header.
labelBaseline	anyOf(TextBaseline, ExprRef)	The vertical text baseline for the header labels. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the titleLineHeight rather than titleFontSize alone.
labelColor	anyOf(Color, ExprRef)	The color of the header label, can be in hex color code or regular color name.
labelExpr	string	Vega expression for customizing labels. Note: The label text and value can be assessed via the label and value properties of the header’s backing datum object.
labelFont	anyOf(string, ExprRef)	The font of the header label.
labelFontSize	anyOf(number, ExprRef)	The font size of the header label, in pixels.
labelFontStyle	anyOf(FontStyle, ExprRef)	The font style of the header label.
labelFontWeight	anyOf(FontWeight, ExprRef)	The font weight of the header label.
labelLimit	anyOf(number, ExprRef)	The maximum length of the header label in pixels. The text value will be automatically truncated if the rendered size exceeds the limit. Default value: 0, indicating no limit
labelLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line header labels or title text with "line-top" or "line-bottom" baseline.
labelOrient	Orient	The orientation of the header label. One of "top", "bottom", "left" or "right".
labelPadding	anyOf(number, ExprRef)	The padding, in pixel, between facet header’s label and the plot. Default value: 10
labels	boolean	A boolean flag indicating if labels should be included as part of the header. Default value: true.
orient	Orient	Shortcut for setting both labelOrient and titleOrient.
title	null	Set to null to disable title for the axis, legend, or header.
titleAlign	anyOf(Align, ExprRef)	Horizontal text alignment (to the anchor) of header titles.
titleAnchor	TitleAnchor	The anchor position for placing the title. One of "start", "middle", or "end". For example, with an orientation of top these anchor positions map to a left-, center-, or right-aligned title.
titleAngle	number	The rotation angle of the header title. Default value: 0.
titleBaseline	anyOf(TextBaseline, ExprRef)	The vertical text baseline for the header title. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the titleLineHeight rather than titleFontSize alone. Default value: "middle"
titleColor	anyOf(Color, ExprRef)	Color of the header title, can be in hex color code or regular color name.
titleFont	anyOf(string, ExprRef)	Font of the header title. (e.g., "Helvetica Neue").
titleFontSize	anyOf(number, ExprRef)	Font size of the header title.
titleFontStyle	anyOf(FontStyle, ExprRef)	The font style of the header title.
titleFontWeight	anyOf(FontWeight, ExprRef)	Font weight of the header title. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
titleLimit	anyOf(number, ExprRef)	The maximum length of the header title in pixels. The text value will be automatically truncated if the rendered size exceeds the limit. Default value: 0, indicating no limit
titleLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line header title text or title text with "line-top" or "line-bottom" baseline.
titleOrient	Orient	The orientation of the header title. One of "top", "bottom", "left" or "right".
titlePadding	anyOf(number, ExprRef)	The padding, in pixel, between facet header’s title and the label. Default value: 10

Legend Configuration

The Chart.configure_legend() allows you to customize the appearance of chart legends, including location, fonts, bounding boxes, colors, and more. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
    color='Origin:N'
)

chart.configure_legend(
    strokeColor='gray',
    fillColor='#EEEEEE',
    padding=10,
    cornerRadius=10,
    orient='top-right'
)

Additional properties are summarized in the following table:

Property	Type	Description
aria	anyOf(boolean, ExprRef)
clipHeight	anyOf(number, ExprRef)
columnPadding	anyOf(number, ExprRef)
columns	anyOf(number, ExprRef)
cornerRadius	anyOf(number, ExprRef)
description	anyOf(string, ExprRef)
direction	Orientation	The direction of the legend, one of "vertical" or "horizontal". Default value: - For top-/bottom-oriented legends, "horizontal" - For left-/right-oriented legends, "vertical" - For top/bottom-left/right-oriented legends, "horizontal" for gradient legends and "vertical" for symbol legends.
disable	boolean	Disable legend by default
fillColor	anyOf(anyOf(null, Color), ExprRef)
gradientDirection	anyOf(Orientation, ExprRef)
gradientHorizontalMaxLength	number	Max legend length for a horizontal gradient when config.legend.gradientLength is undefined. Default value: 200
gradientHorizontalMinLength	number	Min legend length for a horizontal gradient when config.legend.gradientLength is undefined. Default value: 100
gradientLabelLimit	anyOf(number, ExprRef)
gradientLabelOffset	anyOf(number, ExprRef)
gradientLength	anyOf(number, ExprRef)
gradientOpacity	anyOf(number, ExprRef)
gradientStrokeColor	anyOf(anyOf(null, Color), ExprRef)
gradientStrokeWidth	anyOf(number, ExprRef)
gradientThickness	anyOf(number, ExprRef)
gradientVerticalMaxLength	number	Max legend length for a vertical gradient when config.legend.gradientLength is undefined. Default value: 200
gradientVerticalMinLength	number	Min legend length for a vertical gradient when config.legend.gradientLength is undefined. Default value: 100
gridAlign	anyOf(LayoutAlign, ExprRef)
labelAlign	anyOf(Align, ExprRef)
labelBaseline	anyOf(TextBaseline, ExprRef)
labelColor	anyOf(anyOf(null, Color), ExprRef)
labelFont	anyOf(string, ExprRef)
labelFontSize	anyOf(number, ExprRef)
labelFontStyle	anyOf(FontStyle, ExprRef)
labelFontWeight	anyOf(FontWeight, ExprRef)
labelLimit	anyOf(number, ExprRef)
labelOffset	anyOf(number, ExprRef)
labelOpacity	anyOf(number, ExprRef)
labelOverlap	anyOf(LabelOverlap, ExprRef)	The strategy to use for resolving overlap of labels in gradient legends. If false, no overlap reduction is attempted. If set to true or "parity", a strategy of removing every other label is used. If set to "greedy", a linear scan of the labels is performed, removing any label that overlaps with the last visible label (this often works better for log-scaled axes). Default value: "greedy" for log scales otherwise true`.
labelPadding	anyOf(number, ExprRef)
labelSeparation	anyOf(number, ExprRef)
layout	ExprRef
legendX	anyOf(number, ExprRef)
legendY	anyOf(number, ExprRef)
offset	anyOf(number, ExprRef)
orient	LegendOrient	The orientation of the legend, which determines how the legend is positioned within the scene. One of "left", "right", "top", "bottom", "top-left", "top-right", "bottom-left", "bottom-right", "none". Default value: "right"
padding	anyOf(number, ExprRef)
rowPadding	anyOf(number, ExprRef)
strokeColor	anyOf(anyOf(null, Color), ExprRef)
strokeDash	anyOf(array(number), ExprRef)
strokeWidth	anyOf(number, ExprRef)
symbolBaseFillColor	anyOf(anyOf(null, Color), ExprRef)
symbolBaseStrokeColor	anyOf(anyOf(null, Color), ExprRef)
symbolDash	anyOf(array(number), ExprRef)
symbolDashOffset	anyOf(number, ExprRef)
symbolDirection	anyOf(Orientation, ExprRef)
symbolFillColor	anyOf(anyOf(null, Color), ExprRef)
symbolLimit	anyOf(number, ExprRef)
symbolOffset	anyOf(number, ExprRef)
symbolOpacity	anyOf(number, ExprRef)
symbolSize	anyOf(number, ExprRef)
symbolStrokeColor	anyOf(anyOf(null, Color), ExprRef)
symbolStrokeWidth	anyOf(number, ExprRef)
symbolType	anyOf(SymbolShape, ExprRef)
tickCount	anyOf(TickCount, ExprRef)
title	null	Set to null to disable title for the axis, legend, or header.
titleAlign	anyOf(Align, ExprRef)
titleAnchor	anyOf(TitleAnchor, ExprRef)
titleBaseline	anyOf(TextBaseline, ExprRef)
titleColor	anyOf(anyOf(null, Color), ExprRef)
titleFont	anyOf(string, ExprRef)
titleFontSize	anyOf(number, ExprRef)
titleFontStyle	anyOf(FontStyle, ExprRef)
titleFontWeight	anyOf(FontWeight, ExprRef)
titleLimit	anyOf(number, ExprRef)
titleLineHeight	anyOf(number, ExprRef)
titleOpacity	anyOf(number, ExprRef)
titleOrient	anyOf(Orient, ExprRef)
titlePadding	anyOf(number, ExprRef)
unselectedOpacity	number	The opacity of unselected legend entries. Default value: 0.35.
zindex	anyOf(number, ExprRef)

Mark and Mark Style Configuration

The mark configuration can be set using the Chart.configure_mark() method, which sets the default properties for all marks in the chart. In addition, the config object also provides mark-specific configuration using the mark type (e.g. Chart.configure_area()) for defining default properties for each mark.

For general configuration of all mark types, use:

• Chart.configure_mark()

For configurations specific to particular mark types, use:

• Chart.configure_area()

• Chart.configure_bar()

• Chart.configure_circle()

• Chart.configure_geoshape()

• Chart.configure_line()

• Chart.configure_point()

• Chart.configure_rect()

• Chart.configure_rule()

• Chart.configure_square()

• Chart.configure_text()

• Chart.configure_tick()

• Chart.configure_trail()

Each of the above methods accepts the following properties:

Property	Type	Description
align	anyOf(Align, ExprRef)	The horizontal alignment of the text or ranged marks (area, bar, image, rect, rule). One of "left", "right", "center". Note: Expression reference is not supported for range marks.
angle	anyOf(number, ExprRef)
aria	anyOf(boolean, ExprRef)
ariaRole	anyOf(string, ExprRef)
ariaRoleDescription	anyOf(string, ExprRef)
aspect	anyOf(boolean, ExprRef)
baseline	anyOf(TextBaseline, ExprRef)	For text marks, the vertical text baseline. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", "line-bottom", or an expression reference that provides one of the valid values. The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone. For range marks, the vertical alignment of the marks. One of "top", "middle", "bottom". Note: Expression reference is not supported for range marks.
blend	anyOf(Blend, ExprRef)
color	anyOf(Color, Gradient, ExprRef)	Default color. Default value: ■ "#4682b4" Note: - This property cannot be used in a style config. - The fill and stroke properties have higher precedence than color and will override color.
cornerRadius	anyOf(number, ExprRef)
cornerRadiusBottomLeft	anyOf(number, ExprRef)
cornerRadiusBottomRight	anyOf(number, ExprRef)
cornerRadiusTopLeft	anyOf(number, ExprRef)
cornerRadiusTopRight	anyOf(number, ExprRef)
cursor	anyOf(Cursor, ExprRef)
description	anyOf(string, ExprRef)
dir	anyOf(TextDirection, ExprRef)
dx	anyOf(number, ExprRef)
dy	anyOf(number, ExprRef)
ellipsis	anyOf(string, ExprRef)
endAngle	anyOf(number, ExprRef)
fill	anyOf(Color, Gradient, null, ExprRef)	Default fill color. This property has higher precedence than config.color. Set to null to remove fill. Default value: (None)
fillOpacity	anyOf(number, ExprRef)
filled	boolean	Whether the mark’s color should be used as fill color instead of stroke color. Default value: false for all point, line, and rule marks as well as geoshape marks for graticule data sources; otherwise, true. Note: This property cannot be used in a style config.
font	anyOf(string, ExprRef)
fontSize	anyOf(number, ExprRef)
fontStyle	anyOf(FontStyle, ExprRef)
fontWeight	anyOf(FontWeight, ExprRef)
height	anyOf(number, ExprRef)
href	anyOf(URI, ExprRef)
innerRadius	anyOf(number, ExprRef)	The inner radius in pixels of arc marks. innerRadius is an alias for radius2.
interpolate	anyOf(Interpolate, ExprRef)
invalid	[‘filter’, None]	Defines how Vega-Lite should handle marks for invalid values (null and NaN). - If set to "filter" (default), all data items with null values will be skipped (for line, trail, and area marks) or filtered (for other marks). - If null, all data items are included. In this case, invalid values will be interpreted as zeroes.
limit	anyOf(number, ExprRef)
lineBreak	anyOf(string, ExprRef)
lineHeight	anyOf(number, ExprRef)
opacity	anyOf(number, ExprRef)	The overall opacity (value between [0,1]). Default value: 0.7 for non-aggregate plots with point, tick, circle, or square marks or layered bar charts and 1 otherwise.
order	[null, boolean]	For line and trail marks, this order property can be set to null or false to make the lines use the original order in the data sources.
orient	Orientation	The orientation of a non-stacked bar, tick, area, and line charts. The value is either horizontal (default) or vertical. - For bar, rule and tick, this determines whether the size of the bar and tick should be applied to x or y dimension. - For area, this property determines the orient property of the Vega output. - For line and trail marks, this property determines the sort order of the points in the line if config.sortLineBy is not specified. For stacked charts, this is always determined by the orientation of the stack; therefore explicitly specified value will be ignored.
outerRadius	anyOf(number, ExprRef)	The outer radius in pixels of arc marks. outerRadius is an alias for radius.
padAngle	anyOf(number, ExprRef)
radius	anyOf(number, ExprRef)	For arc mark, the primary (outer) radius in pixels. For text marks, polar coordinate radial offset, in pixels, of the text from the origin determined by the x and y properties.
radius2	anyOf(number, ExprRef)	The secondary (inner) radius in pixels of arc marks.
shape	anyOf(anyOf(SymbolShape, string), ExprRef)
size	anyOf(number, ExprRef)	Default size for marks. - For point/circle/square, this represents the pixel area of the marks. Note that this value sets the area of the symbol; the side lengths will increase with the square root of this value. - For bar, this represents the band size of the bar, in pixels. - For text, this represents the font size, in pixels. Default value: - 30 for point, circle, square marks; width/height’s step - 2 for bar marks with discrete dimensions; - 5 for bar marks with continuous dimensions; - 11 for text marks.
smooth	anyOf(boolean, ExprRef)
startAngle	anyOf(number, ExprRef)
stroke	anyOf(Color, Gradient, null, ExprRef)	Default stroke color. This property has higher precedence than config.color. Set to null to remove stroke. Default value: (None)
strokeCap	anyOf(StrokeCap, ExprRef)
strokeDash	anyOf(array(number), ExprRef)
strokeDashOffset	anyOf(number, ExprRef)
strokeJoin	anyOf(StrokeJoin, ExprRef)
strokeMiterLimit	anyOf(number, ExprRef)
strokeOffset	anyOf(number, ExprRef)
strokeOpacity	anyOf(number, ExprRef)
strokeWidth	anyOf(number, ExprRef)
tension	anyOf(number, ExprRef)
text	anyOf(Text, ExprRef)
theta	anyOf(number, ExprRef)	For arc marks, the arc length in radians if theta2 is not specified, otherwise the start arc angle. (A value of 0 indicates up or “north”, increasing values proceed clockwise.) For text marks, polar coordinate angle in radians.
theta2	anyOf(number, ExprRef)	The end angle of arc marks in radians. A value of 0 indicates up or “north”, increasing values proceed clockwise.
timeUnitBand	number	Default relative band size for a time unit. If set to 1, the bandwidth of the marks will be equal to the time unit band step. If set to 0.5, bandwidth of the marks will be half of the time unit band step.
timeUnitBandPosition	number	Default relative band position for a time unit. If set to 0, the marks will be positioned at the beginning of the time unit band step. If set to 0.5, the marks will be positioned in the middle of the time unit band step.
tooltip	anyOf(number, string, boolean, TooltipContent, ExprRef, null)	The tooltip text string to show upon mouse hover or an object defining which fields should the tooltip be derived from. If tooltip is true or {"content": "encoding"}, then all fields from encoding will be used. - If tooltip is {"content": "data"}, then all fields that appear in the highlighted data point will be used. - If set to null or false, then no tooltip will be used. See the tooltip documentation for a detailed discussion about tooltip in Vega-Lite. Default value: null
url	anyOf(URI, ExprRef)
width	anyOf(number, ExprRef)
x	anyOf(number, string, ExprRef)	X coordinates of the marks, or width of horizontal "bar" and "area" without specified x2 or width. The value of this channel can be a number or a string "width" for the width of the plot.
x2	anyOf(number, string, ExprRef)	X2 coordinates for ranged "area", "bar", "rect", and "rule". The value of this channel can be a number or a string "width" for the width of the plot.
y	anyOf(number, string, ExprRef)	Y coordinates of the marks, or height of vertical "bar" and "area" without specified y2 or height. The value of this channel can be a number or a string "height" for the height of the plot.
y2	anyOf(number, string, ExprRef)	Y2 coordinates for ranged "area", "bar", "rect", and "rule". The value of this channel can be a number or a string "height" for the height of the plot.

In addition to the default mark properties above, default values can be further customized using named styles defined as keyword arguments to the Chart.configure_style() method. Styles can then be invoked by including a style property within a mark definition object.

Scale Configuration

Scales can be configured using Chart.configure_scale(), which has the following properties:

Property	Type	Description
bandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band-ordinal scales. Default value: - barBandPaddingInner for bar marks (0.1 by default) - rectBandPaddingInner for rect and other marks (0 by default)
bandPaddingOuter	anyOf(number, ExprRef)	Default outer padding for x and y band-ordinal scales. Default value: paddingInner/2 (which makes width/height = number of unique values * step)
barBandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band-ordinal scales of "bar" marks. Default value: 0.1
clamp	anyOf(boolean, ExprRef)	If true, values that exceed the data domain are clamped to either the minimum or maximum range value
continuousPadding	anyOf(number, ExprRef)	Default padding for continuous scales. Default: 5 for continuous x-scale of a vertical bar and continuous y-scale of a horizontal bar.; 0 otherwise.
maxBandSize	number	The default max value for mapping quantitative fields to bar’s size/bandSize. If undefined (default), we will use the axis’s size (width or height) - 1.
maxFontSize	number	The default max value for mapping quantitative fields to text’s size/fontSize. Default value: 40
maxOpacity	number	Default max opacity for mapping a field to opacity. Default value: 0.8
maxSize	number	Default max value for point size scale.
maxStrokeWidth	number	Default max strokeWidth for the scale of strokeWidth for rule and line marks and of size for trail marks. Default value: 4
minBandSize	number	The default min value for mapping quantitative fields to bar and tick’s size/bandSize scale with zero=false. Default value: 2
minFontSize	number	The default min value for mapping quantitative fields to tick’s size/fontSize scale with zero=false Default value: 8
minOpacity	number	Default minimum opacity for mapping a field to opacity. Default value: 0.3
minSize	number	Default minimum value for point size scale with zero=false. Default value: 9
minStrokeWidth	number	Default minimum strokeWidth for the scale of strokeWidth for rule and line marks and of size for trail marks with zero=false. Default value: 1
pointPadding	anyOf(number, ExprRef)	Default outer padding for x and y point-ordinal scales. Default value: 0.5 (which makes width/height = number of unique values * step)
quantileCount	number	Default range cardinality for quantile scale. Default value: 4
quantizeCount	number	Default range cardinality for quantize scale. Default value: 4
rectBandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band-ordinal scales of "rect" marks. Default value: 0
round	anyOf(boolean, ExprRef)	If true, rounds numeric output values to integers. This can be helpful for snapping to the pixel grid. (Only available for x, y, and size scales.)
useUnaggregatedDomain	boolean	Use the source data range before aggregation as scale domain instead of aggregated data for aggregate axis. This is equivalent to setting domain to "unaggregate" for aggregated quantitative fields by default. This property only works with aggregate functions that produce values within the raw data domain ("mean", "average", "median", "q1", "q3", "min", "max"). For other aggregations that produce values outside of the raw data domain (e.g. "count", "sum"), this property is ignored. Default value: false
xReverse	anyOf(boolean, ExprRef)	Reverse x-scale by default (useful for right-to-left charts).

Scale Range Configuration

Scale ranges can be configured using Chart.configure_range(), which has the following properties:

Property	Type	Description
category	anyOf(RangeScheme, array(Color))	Default color scheme for categorical data.
diverging	anyOf(RangeScheme, array(Color))	Default color scheme for diverging quantitative ramps.
heatmap	anyOf(RangeScheme, array(Color))	Default color scheme for quantitative heatmaps.
ordinal	anyOf(RangeScheme, array(Color))	Default color scheme for rank-ordered data.
ramp	anyOf(RangeScheme, array(Color))	Default color scheme for sequential quantitative ramps.
symbol	array(SymbolShape)	Array of symbol names or paths for the default shape palette.

Projection Configuration

Chart.configure_projection()

Property	Type	Description
center	Vector2<number>	The projection’s center, a two-element array of longitude and latitude in degrees. Default value: [0, 0]
clipAngle	number	The projection’s clipping circle radius to the specified angle in degrees. If null, switches to antimeridian cutting rather than small-circle clipping.
clipExtent	Vector2<Vector2<number>>	The projection’s viewport clip extent to the specified bounds in pixels. The extent bounds are specified as an array [[x0, y0], [x1, y1]], where x0 is the left-side of the viewport, y0 is the top, x1 is the right and y1 is the bottom. If null, no viewport clipping is performed.
coefficient	number
distance	number
extent	Vector2<Vector2<number>>
fit	anyOf(Fit, array(Fit))
fraction	number
lobes	number
parallel	number
parallels	array(number)	For conic projections, the two standard parallels that define the map layout. The default depends on the specific conic projection used.
pointRadius	number	The default radius (in pixels) to use when drawing GeoJSON Point and MultiPoint geometries. This parameter sets a constant default value. To modify the point radius in response to data, see the corresponding parameter of the GeoPath and GeoShape transforms. Default value: 4.5
precision	number	The threshold for the projection’s adaptive resampling to the specified value in pixels. This value corresponds to the Douglas–Peucker distance. If precision is not specified, returns the projection’s current resampling precision which defaults to √0.5 ≅ 0.70710….
radius	number
ratio	number
reflectX	boolean
reflectY	boolean
rotate	anyOf(Vector2<number>, Vector3<number>)	The projection’s three-axis rotation to the specified angles, which must be a two- or three-element array of numbers [lambda, phi, gamma] specifying the rotation angles in degrees about each spherical axis. (These correspond to yaw, pitch and roll.) Default value: [0, 0, 0]
scale	number	The projection’s scale (zoom) factor, overriding automatic fitting. The default scale is projection-specific. The scale factor corresponds linearly to the distance between projected points; however, scale factor values are not equivalent across projections.
size	Vector2<number>
spacing	number
tilt	number
translate	Vector2<number>	The projection’s translation offset as a two-element array [tx, ty].
type	ProjectionType	The cartographic projection to use. This value is case-insensitive, for example "albers" and "Albers" indicate the same projection type. You can find all valid projection types in the documentation. Default value: mercator

Selection Configuration

Chart.configure_selection()

Property	Type	Description
interval	IntervalSelectionConfig	The default definition for an interval selection. All properties and transformations for an interval selection definition (except type) may be specified here. For instance, setting interval to {"translate": false} disables the ability to move interval selections by default.
multi	MultiSelectionConfig	The default definition for a multi selection. All properties and transformations for a multi selection definition (except type) may be specified here. For instance, setting multi to {"toggle": "event.altKey"} adds additional values to multi selections when clicking with the alt-key pressed by default.
single	SingleSelectionConfig	The default definition for a single selection. All properties and transformations for a single selection definition (except type) may be specified here. For instance, setting single to {"on": "dblclick"} populates single selections on double-click by default.

Title Configuration

The Chart.configure_title() method allows configuration of the chart title, including the font, color, placement, and orientation. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
).properties(
    title='Cars Data'
)

chart.configure_title(
    fontSize=20,
    font='Courier',
    anchor='start',
    color='gray'
)

Additional title configuration options are listed in the following table:

Property	Type	Description
align	Align	Horizontal text alignment for title text. One of "left", "center", or "right".
anchor	anyOf(TitleAnchor, ExprRef)
angle	anyOf(number, ExprRef)
aria	anyOf(boolean, ExprRef)
baseline	TextBaseline	Vertical text baseline for title and subtitle text. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone.
color	anyOf(anyOf(null, Color), ExprRef)
dx	anyOf(number, ExprRef)
dy	anyOf(number, ExprRef)
font	anyOf(string, ExprRef)
fontSize	anyOf(number, ExprRef)
fontStyle	anyOf(FontStyle, ExprRef)
fontWeight	anyOf(FontWeight, ExprRef)
frame	anyOf(anyOf(TitleFrame, string), ExprRef)
limit	anyOf(number, ExprRef)
lineHeight	anyOf(number, ExprRef)
offset	anyOf(number, ExprRef)
orient	anyOf(TitleOrient, ExprRef)
subtitleColor	anyOf(anyOf(null, Color), ExprRef)
subtitleFont	anyOf(string, ExprRef)
subtitleFontSize	anyOf(number, ExprRef)
subtitleFontStyle	anyOf(FontStyle, ExprRef)
subtitleFontWeight	anyOf(FontWeight, ExprRef)
subtitleLineHeight	anyOf(number, ExprRef)
subtitlePadding	anyOf(number, ExprRef)
zindex	anyOf(number, ExprRef)

View Configuration

The Chart.configure_view() method allows you to configure aspects of the chart’s view, i.e. the area of the screen in which the data and scales are drawn. Here is an example to demonstrate some of the visual features that can be controlled:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
)

chart.configure_view(
    continuousHeight=200,
    continuousWidth=200,
    strokeWidth=4,
    fill='#FFEEDD',
    stroke='red',
)

Additional properties are summarized in the following table:

Property	Type	Description
clip	boolean	Whether the view should be clipped.
continuousHeight	number	The default height when the plot has a continuous y-field for x or latitude, or has arc marks. Default value: 200
continuousWidth	number	The default width when the plot has a continuous field for x or longitude, or has arc marks. Default value: 200
cornerRadius	anyOf(number, ExprRef)
cursor	Cursor	The mouse cursor used over the view. Any valid CSS cursor type can be used.
discreteHeight	anyOf(number, dict)	The default height when the plot has non arc marks and either a discrete y-field or no y-field. The height can be either a number indicating a fixed height or an object in the form of {step: number} defining the height per discrete step. Default value: a step size based on config.view.step.
discreteWidth	anyOf(number, dict)	The default width when the plot has non-arc marks and either a discrete x-field or no x-field. The width can be either a number indicating a fixed width or an object in the form of {step: number} defining the width per discrete step. Default value: a step size based on config.view.step.
fill	anyOf(Color, null, ExprRef)	The fill color. Default value: undefined
fillOpacity	anyOf(number, ExprRef)
height	number	Default height Deprecated: Since Vega-Lite 4.0. Please use continuousHeight and discreteHeight instead.
opacity	anyOf(number, ExprRef)	The overall opacity (value between [0,1]). Default value: 0.7 for non-aggregate plots with point, tick, circle, or square marks or layered bar charts and 1 otherwise.
step	number	Default step size for x-/y- discrete fields.
stroke	anyOf(Color, null, ExprRef)	The stroke color. Default value: "#ddd"
strokeCap	anyOf(StrokeCap, ExprRef)
strokeDash	anyOf(array(number), ExprRef)
strokeDashOffset	anyOf(number, ExprRef)
strokeJoin	anyOf(StrokeJoin, ExprRef)
strokeMiterLimit	anyOf(number, ExprRef)
strokeOpacity	anyOf(number, ExprRef)
strokeWidth	anyOf(number, ExprRef)
width	number	Default width Deprecated: Since Vega-Lite 4.0. Please use continuousWidth and discreteWidth instead.

Altair Themes

Altair makes available a theme registry that lets users apply chart configurations globally within any Python session. This is done via the alt.themes object.

The themes registry consists of functions which define a specification dictionary that will be added to every created chart. For example, the default theme configures the default size of a single chart:

>>> import altair as alt
>>> default = alt.themes.get()
>>> default()
{'config': {'view': {'continuousWidth': 400, 'continuousHeight': 300}}}

You can see that any chart you create will have this theme applied, and these configurations added to its specification:

import altair as alt
from vega_datasets import data

chart = alt.Chart(data.cars.url).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q'
)

chart.to_dict()

    {'config': {'view': {'continuousWidth': 400, 'continuousHeight': 300}}, 'data': {'url': 'https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/cars.json'}, 'mark': 'point', 'encoding': {'x': {'field': 'Horsepower', 'type': 'quantitative'}, 'y': {'field': 'Miles_per_Gallon', 'type': 'quantitative'}}, '$schema': 'https://vega.github.io/schema/vega-lite/v4.17.0.json'}

The rendered chart will then reflect these configurations:

chart

Changing the Theme

If you would like to enable any other theme for the length of your Python session, you can call alt.themes.enable(theme_name). For example, Altair includes a theme in which the chart background is opaque rather than transparent:

alt.themes.enable('opaque')
chart.to_dict()

    {'config': {'background': 'white', 'view': {'continuousWidth': 400, 'continuousHeight': 300}}, 'data': {'url': 'https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/cars.json'}, 'mark': 'point', 'encoding': {'x': {'field': 'Horsepower', 'type': 'quantitative'}, 'y': {'field': 'Miles_per_Gallon', 'type': 'quantitative'}}, '$schema': 'https://vega.github.io/schema/vega-lite/v4.17.0.json'}

chart

Notice that the background color of the chart is now set to white. If you would like no theme applied to your chart, you can use the theme named 'none':

alt.themes.enable('none')
chart.to_dict()

    {'data': {'url': 'https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/cars.json'}, 'mark': 'point', 'encoding': {'x': {'field': 'Horsepower', 'type': 'quantitative'}, 'y': {'field': 'Miles_per_Gallon', 'type': 'quantitative'}}, '$schema': 'https://vega.github.io/schema/vega-lite/v4.17.0.json'}

chart

Because the view configuration is not set, the chart is smaller than the default rendering.

If you would like to use any theme just for a single chart, you can use the with statement to enable a temporary theme:

with alt.themes.enable('default'):
    spec = chart.to_json()

Currently Altair does not offer many built-in themes, but we plan to add more options in the future.

Defining a Custom Theme

The theme registry also allows defining and registering custom themes. A theme is simply a function that returns a dictionary of default values to be added to the chart specification at rendering time, which is then registered and activated.

For example, here we define a theme in which all marks are drawn with black fill unless otherwise specified:

import altair as alt
from vega_datasets import data

# define the theme by returning the dictionary of configurations
def black_marks():
    return {
        'config': {
            'view': {
                'height': 300,
                'width': 400,
            },
            'mark': {
                'color': 'black',
                'fill': 'black'
            }
        }
    }

# register the custom theme under a chosen name
alt.themes.register('black_marks', black_marks)

# enable the newly registered theme
alt.themes.enable('black_marks')

# draw the chart
cars = data.cars.url
alt.Chart(cars).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q'
)

If you want to restore the default theme, use:

alt.themes.enable('default')

For more ideas on themes, see the Vega Themes repository.