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A client for quickchart.io, a service that generates static chart images

Project description

quickchart-python

Build Status PyPI PyPI - License

A Python client for the quickchart.io image charts web service.

Installation

Use the quickchart library in this project, or install through pip:

pip install quickchart.io

Usage

This library provides a QuickChart class. Import and instantiate it. Then set properties on it and specify a Chart.js config:

from quickchart import QuickChart

qc = QuickChart()
qc.width = 500
qc.height = 300
qc.config = {
    "type": "bar",
    "data": {
        "labels": ["Hello world", "Test"],
        "datasets": [{
            "label": "Foo",
            "data": [1, 2]
        }]
    }
}

Use get_url() on your quickchart object to get the encoded URL that renders your chart:

print(qc.get_url())
# https://quickchart.io/chart?c=%7B%22chart%22%3A+%7B%22type%22%3A+%22bar%22%2C+%22data%22%3A+%7B%22labels%22%3A+%5B%22Hello+world%22%2C+%22Test%22%5D%2C+%22datasets%22%3A+%5B%7B%22label%22%3A+%22Foo%22%2C+%22data%22%3A+%5B1%2C+2%5D%7D%5D%7D%7D%7D&w=600&h=300&bkg=%23ffffff&devicePixelRatio=2.0&f=png

If you have a long or complicated chart, use get_short_url() to get a fixed-length URL using the quickchart.io web service (note that these URLs only persist for a short time unless you have a subscription):

print(qc.get_short_url())
# https://quickchart.io/chart/render/f-a1d3e804-dfea-442c-88b0-9801b9808401

The URLs will render an image of a chart:

Using Javascript functions in your chart

Chart.js sometimes relies on Javascript functions (e.g. for formatting tick labels). There are a couple approaches:

  • Build chart configuration as a string instead of a Python object. See examples/simple_example_with_function.py.
  • Build chart configuration as a Python object and include a placeholder string for the Javascript function. Then, find and replace it.
  • Use the provided QuickChartFunction class. See examples/using_quickchartfunction.py for a full example.

A short example using QuickChartFunction:

qc = QuickChart()
qc.config = {
    "type": "bar",
    "data": {
        "labels": ["A", "B"],
        "datasets": [{
            "label": "Foo",
            "data": [1, 2]
        }]
    },
    "options": {
        "scales": {
            "yAxes": [{
                "ticks": {
                    "callback": QuickChartFunction('(val) => val + "k"')
                }
            }],
            "xAxes": [{
                "ticks": {
                    "callback": QuickChartFunction('''function(val) {
                      return val + '???';
                    }''')
                }
            }]
        }
    }
}

print(qc.get_url())

Customizing your chart

You can set the following properties:

config: dict or str

The actual Chart.js chart configuration.

width: int

Width of the chart image in pixels. Defaults to 500

height: int

Height of the chart image in pixels. Defaults to 300

format: str

Format of the chart. Defaults to png. svg is also valid.

background_color: str

The background color of the chart. Any valid HTML color works. Defaults to #ffffff (white). Also takes rgb, rgba, and hsl values.

device_pixel_ratio: float

The device pixel ratio of the chart. This will multiply the number of pixels by the value. This is usually used for retina displays. Defaults to 1.0.

version: str

The version of Chart.js to use. Acceptable values are documented here. Usually used to select Chart.js 3+.

host

Override the host of the chart render server. Defaults to quickchart.io.

key

Set an API key that will be included with the request.

Getting URLs

There are two ways to get a URL for your chart object.

get_url(): str

Returns a URL that will display the chart image when loaded.

get_short_url(): str

Uses the quickchart.io web service to create a fixed-length chart URL that displays the chart image. Returns a URL such as https://quickchart.io/chart/render/f-a1d3e804-dfea-442c-88b0-9801b9808401.

Note that short URLs expire after a few days for users of the free service. You can subscribe to keep them around longer.

Other functionality

get_bytes()

Returns the bytes representing the chart image.

to_file(path: str)

Writes the chart image to a file path.

More examples

Checkout the examples directory to see other usage.

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