Plugins¶
Datasette’s plugin system is currently under active development. It allows additional features to be implemented as Python code (or front-end JavaScript) which can be wrapped up in a separate Python package. The underlying mechanism uses pluggy.
You can follow the development of plugins in issue #14.
Using plugins¶
If a plugin has been packaged for distribution using setuptools you can use the plugin by installing it alongside Datasette in the same virtual environment or Docker container.
You can also define one-off per-project plugins by saving them as
plugin_name.py
functions in a plugins/
folder and then passing that
folder to datasette serve
.
The datasette publish
and datasette package
commands both take an
optional --install
argument. You can use this one or more times to tell
Datasette to pip install
specific plugins as part of the process. You can
use the name of a package on PyPI or any of the other valid arguments to pip
install
such as a URL to a .zip
file:
datasette publish now mydb.db \
--install=datasette-plugin-demos \
--install=https://url-to-my-package.zip
Writing plugins¶
The easiest way to write a plugin is to create a my_plugin.py
file and
drop it into your plugins/
directory. Here is an example plugin, which
adds a new custom SQL function called hello_world()
which takes no
arguments and returns the string Hello world!
.
from datasette import hookimpl
@hookimpl
def prepare_connection(conn):
conn.create_function('hello_world', 0, lambda: 'Hello world!')
If you save this in plugins/my_plugin.py
you can then start Datasette like
this:
datasette serve mydb.db --plugins-dir=plugins/
Now you can navigate to http://localhost:8001/mydb and run this SQL:
select hello_world();
To see the output of your plugin.
Packaging a plugin¶
Plugins can be packaged using Python setuptools. You can see an example of a packaged plugin at https://github.com/simonw/datasette-plugin-demos
The example consists of two files: a setup.py
file that defines the plugin:
from setuptools import setup
VERSION = '0.1'
setup(
name='datasette-plugin-demos',
description='Examples of plugins for Datasette',
author='Simon Willison',
url='https://github.com/simonw/datasette-plugin-demos',
license='Apache License, Version 2.0',
version=VERSION,
py_modules=['datasette_plugin_demos'],
entry_points={
'datasette': [
'plugin_demos = datasette_plugin_demos'
]
},
install_requires=['datasette']
)
And a Python module file, datasette_plugin_demos.py
, that implements the
plugin:
from datasette import hookimpl
import random
@hookimpl
def prepare_jinja2_environment(env):
env.filters['uppercase'] = lambda u: u.upper()
@hookimpl
def prepare_connection(conn):
conn.create_function('random_integer', 2, random.randint)
Having built a plugin in this way you can turn it into an installable package using the following command:
python3 setup.py sdist
This will create a .tar.gz
file in the dist/
directory.
You can then install your new plugin into a Datasette virtual environment or
Docker container using pip
:
pip install datasette-plugin-demos-0.1.tar.gz
To learn how to upload your plugin to PyPI for use by other people, read the PyPA guide to Packaging and distributing projects.
Static assets¶
If your plugin has a static/
directory, Datasette will automatically
configure itself to serve those static assets from the following path:
/-/static-plugins/NAME_OF_PLUGIN_PACKAGE/yourfile.js
See the datasette-plugin-demos repository for an example of how to create a package that includes a static folder.
Custom templates¶
If your plugin has a templates/
directory, Datasette will attempt to load
templates from that directory before it uses its own default templates.
The priority order for template loading is:
- templates from the
--template-dir
argument, if specified - templates from the
templates/
directory in any installed plugins - default templates that ship with Datasette
See Customization for more details on how to write custom templates, including which filenames to use to customize which parts of the Datasette UI.
Plugin hooks¶
Datasette will eventually have many more plugin hooks. You can track and contribute to their development in issue #14.
prepare_connection(conn)¶
This hook is called when a new SQLite database connection is created. You can use it to register custom SQL functions, aggregates and collations. For example:
from datasette import hookimpl
import random
@hookimpl
def prepare_connection(conn):
conn.create_function('random_integer', 2, random.randint)
This registers a SQL function called random_integer
which takes two
arguments and can be called like this:
select random_integer(1, 10);
prepare_jinja2_environment(env)¶
This hook is called with the Jinja2 environment that is used to evaluate Datasette HTML templates. You can use it to do things like register custom template filters, for example:
from datasette import hookimpl
@hookimpl
def prepare_jinja2_environment(env):
env.filters['uppercase'] = lambda u: u.upper()
You can now use this filter in your custom templates like so:
Table name: {{ table|uppercase }}
extra_css_urls()¶
Return a list of extra CSS URLs that should be included on every page. These can take advantage of the CSS class hooks described in Customization.
This can be a list of URLs:
from datasette import hookimpl
@hookimpl
def extra_css_urls():
return [
'https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css'
]
Or a list of dictionaries defining both a URL and an SRI hash:
from datasette import hookimpl
@hookimpl
def extra_css_urls():
return [{
'url': 'https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css',
'sri': 'sha384-9gVQ4dYFwwWSjIDZnLEWnxCjeSWFphJiwGPXr1jddIhOegiu1FwO5qRGvFXOdJZ4',
}]
extra_js_urls()¶
This works in the same way as extra_css_urls()
but for JavaScript. You can
return either a list of URLs or a list of dictionaries:
from datasette import hookimpl
@hookimpl
def extra_js_urls():
return [{
'url': 'https://code.jquery.com/jquery-3.3.1.slim.min.js',
'sri': 'sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo',
}]
You can also return URLs to files from your plugin’s static/
directory, if
you have one:
from datasette import hookimpl
@hookimpl
def extra_js_urls():
return [
'/-/static-plugins/your_plugin/app.js'
]