Format Charts in Presentations Using Python

What this page is about

Learn chart formatting in Aspose.Slides for Python via .NET and elevate your PowerPoint presentation with custom axes, fonts, number formats, and rounded chart borders.

Overview

This article explains how to format charts in PowerPoint presentations by using Aspose.Slides. It shows how to customize key chart elements such as axes, grid lines, titles, legends, the plot area, and wall fills to improve the appearance and readability of chart data.

It also demonstrates how to set font properties for chart text, apply preset numeric formats to chart data, and enable rounded corners for the chart area. Together, these examples show how to control both the visual style and data presentation of charts in a presentation.

Format Chart Entities

Use Chart to format chart titles, axes, grid lines, legends, and the plot area. This example creates a line chart with markers and default data, then applies separate text and line styles to its value and category axes. Font sizes and line widths are specified in points; category labels are rotated by 45 degrees.

The value axis uses number_format independently of the source cells. Its scale runs from -2 to 15, with major intervals of 2 and minor intervals of 0.5. The example also combines percentage formatting with display_unit set to thousands, so adapt these settings to the meaning and magnitude of your data. The legend stays outside the plot area because overlay is disabled. Back-wall and floor fills are configured through back_wall and floor, but these surfaces are only visible in 3D charts.

import aspose.slides.charts as charts
import aspose.slides as slides

with slides.Presentation() as presentation:

    slide = presentation.slides[0]

    chart = slide.shapes.add_chart(charts.ChartType.LINE_WITH_MARKERS, 50, 50, 500, 400)

    chart.has_title = True
    chart.chart_title.add_text_frame_for_overriding("")
    chart_title = chart.chart_title.text_frame_for_overriding.paragraphs[0].portions[0]
    chart_title.text = "Sample Chart"
    chart_title.portion_format.fill_format.fill_type = slides.FillType.SOLID
    chart_title.portion_format.fill_format.solid_fill_color.color = slides.Color.gray
    chart_title.portion_format.font_height = 20
    chart_title.portion_format.font_bold = slides.NullableBool.TRUE
    chart_title.portion_format.font_italic = slides.NullableBool.TRUE

    chart.axes.vertical_axis.major_grid_lines_format.line.fill_format.fill_type = slides.FillType.SOLID
    chart.axes.vertical_axis.major_grid_lines_format.line.fill_format.solid_fill_color.color = slides.Color.blue
    chart.axes.vertical_axis.major_grid_lines_format.line.width = 5
    chart.axes.vertical_axis.major_grid_lines_format.line.dash_style = slides.LineDashStyle.DASH_DOT

    chart.axes.vertical_axis.minor_grid_lines_format.line.fill_format.fill_type = slides.FillType.SOLID
    chart.axes.vertical_axis.minor_grid_lines_format.line.fill_format.solid_fill_color.color = slides.Color.red
    chart.axes.vertical_axis.minor_grid_lines_format.line.width = 3

    chart.axes.vertical_axis.is_number_format_linked_to_source = False
    chart.axes.vertical_axis.display_unit = charts.DisplayUnitType.THOUSANDS
    chart.axes.vertical_axis.number_format = "0.0%"

    chart.axes.vertical_axis.is_automatic_major_unit = False
    chart.axes.vertical_axis.is_automatic_max_value = False
    chart.axes.vertical_axis.is_automatic_minor_unit = False
    chart.axes.vertical_axis.is_automatic_min_value = False

    chart.axes.vertical_axis.max_value = 15
    chart.axes.vertical_axis.min_value = -2
    chart.axes.vertical_axis.minor_unit = 0.5
    chart.axes.vertical_axis.major_unit = 2.0

    vertical_axis_portion_format = chart.axes.vertical_axis.text_format.portion_format
    vertical_axis_portion_format.font_bold = slides.NullableBool.TRUE
    vertical_axis_portion_format.font_height = 16
    vertical_axis_portion_format.font_italic = slides.NullableBool.TRUE
    vertical_axis_portion_format.fill_format.fill_type = slides.FillType.SOLID
    vertical_axis_portion_format.fill_format.solid_fill_color.color = slides.Color.dark_green
    vertical_axis_portion_format.latin_font = slides.FontData("Times New Roman")

    chart.axes.vertical_axis.has_title = True
    chart.axes.vertical_axis.title.add_text_frame_for_overriding("")
    vertical_axis_title = chart.axes.vertical_axis.title.text_frame_for_overriding.paragraphs[0].portions[0]
    vertical_axis_title.text = "Primary Axis"
    vertical_axis_title.portion_format.fill_format.fill_type = slides.FillType.SOLID
    vertical_axis_title.portion_format.fill_format.solid_fill_color.color = slides.Color.gray
    vertical_axis_title.portion_format.font_height = 20
    vertical_axis_title.portion_format.font_bold = slides.NullableBool.TRUE
    vertical_axis_title.portion_format.font_italic = slides.NullableBool.TRUE

    chart.axes.horizontal_axis.major_grid_lines_format.line.fill_format.fill_type = slides.FillType.SOLID
    chart.axes.horizontal_axis.major_grid_lines_format.line.fill_format.solid_fill_color.color = slides.Color.green
    chart.axes.horizontal_axis.major_grid_lines_format.line.width = 5

    chart.axes.horizontal_axis.minor_grid_lines_format.line.fill_format.fill_type = slides.FillType.SOLID
    chart.axes.horizontal_axis.minor_grid_lines_format.line.fill_format.solid_fill_color.color = slides.Color.yellow
    chart.axes.horizontal_axis.minor_grid_lines_format.line.width = 3

    horizontal_axis_portion_format = chart.axes.horizontal_axis.text_format.portion_format
    horizontal_axis_portion_format.font_bold = slides.NullableBool.TRUE
    horizontal_axis_portion_format.font_height = 16
    horizontal_axis_portion_format.font_italic = slides.NullableBool.TRUE
    horizontal_axis_portion_format.fill_format.fill_type = slides.FillType.SOLID
    horizontal_axis_portion_format.fill_format.solid_fill_color.color = slides.Color.blue
    horizontal_axis_portion_format.latin_font = slides.FontData("Arial")

    chart.axes.horizontal_axis.has_title = True
    chart.axes.horizontal_axis.title.add_text_frame_for_overriding("")

    horizontal_axis_title = chart.axes.horizontal_axis.title.text_frame_for_overriding.paragraphs[0].portions[0]
    horizontal_axis_title.text = "Sample Category"
    horizontal_axis_title.portion_format.fill_format.fill_type = slides.FillType.SOLID
    horizontal_axis_title.portion_format.fill_format.solid_fill_color.color = slides.Color.gray
    horizontal_axis_title.portion_format.font_height = 20
    horizontal_axis_title.portion_format.font_bold = slides.NullableBool.TRUE
    horizontal_axis_title.portion_format.font_italic = slides.NullableBool.TRUE

    chart.axes.horizontal_axis.tick_label_position = charts.TickLabelPositionType.LOW

    chart.axes.horizontal_axis.tick_label_rotation_angle = 45

    legend_portion_format = chart.legend.text_format.portion_format
    legend_portion_format.font_bold = slides.NullableBool.TRUE
    legend_portion_format.font_height = 16
    legend_portion_format.font_italic = slides.NullableBool.TRUE
    legend_portion_format.fill_format.fill_type = slides.FillType.SOLID
    legend_portion_format.fill_format.solid_fill_color.color = slides.Color.dark_red

    chart.legend.overlay = False

    chart.back_wall.thickness = 1
    chart.back_wall.format.fill.fill_type = slides.FillType.SOLID
    chart.back_wall.format.fill.solid_fill_color.color = slides.Color.orange

    chart.floor.format.fill.fill_type = slides.FillType.SOLID
    chart.floor.format.fill.solid_fill_color.color = slides.Color.red

    chart.plot_area.format.fill.fill_type = slides.FillType.SOLID
    chart.plot_area.format.fill.solid_fill_color.color = slides.Color.light_cyan

    presentation.save("FormattedChart.pptx", slides.export.SaveFormat.PPTX)

Set Font Properties for a Chart

Set the default font size for chart text through Chart.text_format. The example creates a clustered column chart with a 20-point font and enables value labels for the first series through show_value. Text elements with their own explicit font settings can override the chart default.

import aspose.slides.charts as charts
import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]

    chart = slide.shapes.add_chart(charts.ChartType.CLUSTERED_COLUMN, 100, 100, 500, 400)
    chart.text_format.portion_format.font_height = 20
    chart.chart_data.series[0].labels.default_data_label_format.show_value = True

    presentation.save("ChartFontProperties.pptx", slides.export.SaveFormat.PPTX)

Set the Numeric Format

Use ChartDataCell.preset_number_format to apply a built-in number format to chart workbook cells. This example creates a clustered column chart with default, cell-backed data and applies format index 10 (0.00%) to each series value cell. This changes how the values are displayed in the workbook without changing the underlying numbers; for example, 0.25 is displayed as 25.00%. Axis and data-label formats can be configured separately.

import aspose.slides.charts as charts
import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]

    chart = slide.shapes.add_chart(charts.ChartType.CLUSTERED_COLUMN, 50, 50, 500, 400)

    for series in chart.chart_data.series:
        for data_point in series.data_points:
            data_point.value.as_cell.preset_number_format = 10  # 0.00%

    presentation.save("PresetNumberFormat.pptx", slides.export.SaveFormat.PPTX)

The following table lists built-in number format indices with representative Excel formats for the English (United States) locale. The exact format strings and their display can vary by application and locale, particularly for currency and dates. Some Excel formats also differ from the defaults in the OOXML standard, as described in Microsoft’s number format implementation notes.

Index	Format
0	`General`
1	`0`
2	`0.00`
3	`#,##0`
4	`#,##0.00`
5	`"$"#,##0_);("$"#,##0)`
6	`"$"#,##0_);[Red]("$"#,##0)`
7	`"$"#,##0.00_);("$"#,##0.00)`
8	`"$"#,##0.00_);[Red]("$"#,##0.00)`
9	`0%`
10	`0.00%`
11	`0.00E+00`
12	`# ?/?`
13	`# ??/??`
14	`m/d/yyyy`
15	`d-mmm-yy`
16	`d-mmm`
17	`mmm-yy`
18	`h:mm AM/PM`
19	`h:mm:ss AM/PM`
20	`h:mm`
21	`h:mm:ss`
22	`m/d/yyyy h:mm`
37	`#,##0_);(#,##0)`
38	`#,##0_);[Red](#,##0)`
39	`#,##0.00_);(#,##0.00)`
40	`#,##0.00_);[Red](#,##0.00)`
41	`_(* #,##0_);_(* (#,##0);_(* "-"_);_(@_)`
42	`_("$"* #,##0_);_("$"* (#,##0);_("$"* "-"_);_(@_)`
43	`_(* #,##0.00_);_(* (#,##0.00);_(* "-"??_);_(@_)`
44	`_("$"* #,##0.00_);_("$"* (#,##0.00);_("$"* "-"??_);_(@_)`
45	`mm:ss`
46	`[h]:mm:ss`
47	`mm:ss.0`
48	`##0.0E+0`
49	`@`

Set Chart Area Rounded Borders

Enable Chart.has_rounded_corners to round the corners of the chart area. The example creates a clustered column chart and uses line_format to give its outline a solid gray color and a single-line style before saving the presentation.

import aspose.slides.charts as charts
import aspose.slides as slides

with slides.Presentation() as presentation:
    slide = presentation.slides[0]

    chart = slide.shapes.add_chart(charts.ChartType.CLUSTERED_COLUMN, 20, 100, 600, 400)
    chart.line_format.fill_format.fill_type = slides.FillType.SOLID
    chart.line_format.fill_format.solid_fill_color.color = slides.Color.gray
    chart.line_format.style = slides.LineStyle.SINGLE
    chart.has_rounded_corners = True

    presentation.save("RoundedBorders.pptx", slides.export.SaveFormat.PPTX)

Edit Existing Chart Annotations

A chart can contain custom shapes, such as a text annotation explaining the status of a report. Access these shapes through Chart.user_shapes. Its shapes collection contains the chart-owned shapes.

An ordinary text box placed over a chart belongs to the slide, even if it looks like part of the chart. Iterating through Slide.shapes finds the chart and ordinary slide shapes, but does not enumerate the individual shapes inside the chart. Chart titles and data labels are separate chart elements, not custom annotations in this collection.

Download chart-annotations.pptx and place it in the application’s working directory. Its first slide contains a chart with an ungrouped annotation reading “Preliminary results”, a chart-owned line, and an ordinary slide text box reading “Slide overlay”. The example finds the first chart on that slide and changes the annotation to “Final results” when the report is ready to publish. It checks for an empty collection and only edits an AutoShape with a text_frame that is not None and contains the expected text.

import aspose.slides as slides
import aspose.slides.charts as charts

with slides.Presentation("chart-annotations.pptx") as presentation:
    slide = presentation.slides[0]
    chart = next((shape for shape in slide.shapes if isinstance(shape, charts.Chart)), None)

    if chart is None or len(chart.user_shapes.shapes) == 0:
        print("No chart or chart-owned shapes found.")
    else:
        updated = False
        for shape in chart.user_shapes.shapes:
            if isinstance(shape, slides.AutoShape) and shape.text_frame is not None:
                if shape.text_frame.text == "Preliminary results":
                    shape.text_frame.text = "Final results"
                    updated = True
                    break

        if updated:
            presentation.save("chart-annotations-updated.pptx", slides.export.SaveFormat.PPTX)
        else:
            print("No matching text annotation found.")

The line and the slide text box remain unchanged. The following images show the input and the saved, reopened result:

Before editing	After editing

Note

The example inspects only the top-level chart-owned shapes. If an annotation is inside a GroupShape, inspect that group’s shapes collection as well. Repeat this recursively for nested groups, applying the same text checks to their child shapes. A group itself is a container; do not treat it as a text box.

FAQ

Can I set semi-transparent fills for columns/areas while keeping the border opaque?

Yes. Fill transparency and the outline are configured separately. This is useful for improving the readability of the grid and data in dense visualizations.

How can I deal with data labels when they overlap?

Reduce the font size, disable nonessential label components (for example, categories), adjust the label position, show labels only for selected points if necessary, or switch the format to “value + legend”.

Can I apply gradient or pattern fills to series?

Yes. Series support solid, gradient, and pattern fills. In practice, use gradients sparingly and avoid combinations that reduce contrast with the grid and text.

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