Entry Points

What is an Entry Point?

The setuptools package to which pip is a frontend has a feature called entry points. When a distribution which registers entry points is installed, the entry point specifications are written to a file inside the distribution’s .egg-info folder. setuptools provides a package pkg_resources which can find these entry points by distribution, group and/or name and load the data structure to which it points.

This is the way AiiDA finds and loads classes provided by plugins.

AiiDA Entry Points

This document contains a list of entry point groups AiiDA uses, with an example usage for each. In the following, we assume the following folder structure:

aiida-mycode/           - distribution folder
   aiida_mycode/        - toplevel package (from aiida_myplug import ..)
      __init__.py
      calcs/
         __init__.py
         mycode.py      - contains MycodeCalculation
      parsers/
         __init__.py
         mycode.py      - contains MycodeParser
      data/
         __init__.py
         mydat.py       - contains MyData (supports code specific format)
      commands/
         __init__.py
         mydat.py       - contains visualization subcommand for MyData
      workflows/
         __init__.py
         mywf.py        - contains a basic workflow using mycode
      ...
   setup.py             - install script
   setup.json           - install configuration
   ...

For a plugin that uses this folder structure, see the aiida plugin template.

Note, however, that the folder structure inside aiida-mycode/ is entirely up to you. A very simple plugin might look like:

aiida-mysimple/
   aiida_mysimple/
      __init__.py
      simpledata.py
   setup.py
   setup.json

The plugin has to tell AiiDA where to look for the classes to be used as calculations, parsers, transports, etc. This is done inside setup.json by way of the entry_points keyword:

...
entry_points={
   <Entry Point Group>: [
      <Entry Point Specification>,
      ...
   ],
...

It is given as a dictionary containing entry point group names as keywords. The list for each entry point group contains entry point specifications.

A specification in turn is given as a string and consists of two parts, a name and an import path describing where the class is to be imported from. The two parts are sparated by an = sign:

"mycode.mydat = aiida_mycode.data.mydat:MyData"

We strongly suggest to start the name of each entry point with the name of the plugin, ommitting the leading ‘aiida-‘. In our example this leads to entry specifications like "mycode.<any.you.want> = <module.path:class>", just like the above example. Exceptions to this rule are schedulers, transports and potentially data ones. Further exceptions can be tolerated in order to provide backwards compatibility if the plugin was in use before aiida-0.9 and its modules were installed in locations which does not make it possible to follow this rule.

Below, a list of valid entry points recognized by AiiDA follows.

aiida.calculations

Entry points in this group are expected to be subclasses of aiida.orm.JobCalculation. This replaces the previous method of placing a python module with the class in question inside the aiida/orm/calculation/job subpackage.

Example entry point specification:

entry_points={
   "aiida.calculations": [
      "mycode.mycode = aiida_mycode.calcs.mycode:MycodeCalculation"
   ]
}

aiida_mycode/calcs/mycode.py:

from aiida.orm import JobCalculation
class MycodeCalculation(JobCalculation):
   ...

Will lead to usage:

from aiida.plugins import CalculationFactory
calc = CalculationFactory('mycode.mycode')

aiida.parsers

Aiida expects a subclass of Parser. Replaces the previous approach consisting in placing a parser module under aiida/parsers/plugins.

Example spec:

entry_points={
   "aiida.calculations": [
      "mycode.mycode = aiida_mycode.parsers.mycode:MycodeParser"
   ]
}

aida_mycode/parsers/myparser.py:

from aiida.parsers import Parser
class MycodeParser(Parser)
   ...

Usage:

from aiida.plugins import ParserFactory
parser = ParserFactory('mycode.mycode')

aiida.data

Group for Data subclasses. Previously located in a subpackage of aiida/orm/data.

Spec:

entry_points={
   "aiida.data": [
      "mycode.mydata = aiida_mycode.data.mydat:MyData"
   ]
}

aiida_mycode/data/mydat.py:

from aiida.orm import Data
class MyData(Data):
   ...

Usage:

from aiida.plugins import DataFactory
params = DataFactory('mycode.mydata')

aiida.workflows

For AiiDA workflows. Instead of putting a workflow somewhere under the aiida.workflows package, it can now be packaged as a plugin and exposed to aiida as follows:

Spec:

entry_points={
   "aiida.workflows": [
      "mycode.mywf = aiida_mycode.workflows.mywf:MyWorkflow"
   ]
}

aiida_mycode/workflows/mywf.py:

from aiida.engine.workchain import WorkChain
class MyWorkflow(WorkChain):
   ...

Usage:

from aiida.plugins import WorkflowFactory
wf = WorkflowFactory('mycode.mywf')

Note

For old-style workflows the entry point mechanism of the plugin system is not supported. Therefore one cannot load these workflows with the WorkflowFactory. The only way to run these, is to store their source code in the aiida/workflows/user directory and use normal python imports to load the classes.

aiida.cmdline

For subcommands to verdi commands like verdi data mydata. Plugin support for commands is possible due to using click. AiiDA expects each entry point to be either a click.Command or click.CommandGroup.

Spec:

entry_points={
   "aiida.cmdline.data": [
      "mydata = aiida_mycode.commands.mydata:mydata"
   ]
}

aiida_mycode/commands/mydata.py:

import click
@click.group()
mydata():
   """commandline help for mydata command"""

@mydata.command('animate')
@click.option('--format')
@click.argument('pk')
create_fancy_animation(format, pk):
   """help"""
   ...

Usage:

verdi data mydata animate --format=Format PK

aiida.tools.dbexporters

If your plugin adds support for exporting to an external database, use this entry point to have aiida find the module where you define the necessary functions.

aiida.tools.dbimporters

If your plugin adds support for importing from an external database, use this entry point to have aiida find the module where you define the necessary functions.

aiida.schedulers

For scheduler plugins. Note that the entry point name is not prefixed by the plugin name. This is because typically a scheduler should be distributed in a plugin on its own, and only one plugin per scheduler should be necessary.

Spec:

entry_points={
   "aiida.schedulers": [
      "myscheduler = aiida_myscheduler.myscheduler:MyScheduler"
   ]
}

aiida_myscheduler/myscheduler.py:

from aiida.schedulers import Scheduler
class MyScheduler(Scheduler):
   ...

Usage: The scheduler is used in the familiar way by entering ‘myscheduler’ as the scheduler option when setting up a computer.

aiida.transports

Like schedulers, transports are supposed to be distributed in a separate plugin. Therefore we will again omit the plugin’s name in the entry point name.

Spec:

entry_points={
   "aiida.transports": [
      "mytransport = aiida_mytransport.mytransport:MyTransport"
   ]
}

aiida_mytransport/mytransport.py:

from aiida.transports import Transport
class MyTransport(Transport):
   ...

Usage:

from aiida.plugins import TransportFactory
transport = TransportFactory('mytransport')

Jus like one would expect, when a computer is setup, mytransport can be given as the transport option.