Tutorial

Using PyCha is quite simple. You always follow the same 5 simple steps:

1. Create a Cairo surface to draw the chart on.
2. Build a list of data sets from which your chart will be created.
3. Customize the chart options.
4. Create the chart, add the datasets, and render it.
5. Save the results into a file or do whatever you want with the Cairo surface.

Creating a Cairo Surface

Detailed information on the Cairo library can be found on their website.

To create the Cairo surface, you need to specify the type of surface and its dimensions:

import cairo
width, height = (500, 400)
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)

Building Datasets

PyCha requires a dataset in the form:

dataSet = (
     ('dataSet 1', ((0, 1), (1, 3), (2, 2.5))),
     ('dataSet 2', ((0, 2), (1, 4), (2, 3))),
     ('dataSet 3', ((0, 5), (1, 1), (2, 0.5))),
)

Each data set is a tuple, of which the first element is the name of the data set and the second is a tuple of two points (x, y).

Customizing Options

Please refer to Changing Defaults.

Create and Render Chart

Now we are ready to instantiate the chart, add the dataset, and render it:

import pycha.bar
chart = pycha.bar.VerticalBarChart(surface, options)
chart.addDataset(dataSet)
chart.render()

Please see PyCha chart types for supported outputs.

Saving Results

Finally, you can write the surface to a file using the Cairo library:

surface.write_to_png('output.png')

That’s it! Please see Ex1: Save Chart to File and Ex2: Embed Chart in GTK App for examples.