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Hello world
===========
This script demonstrates how to define an Ewoks workflow from the ground up. The only thing needed to run it is the ``ewoks`` Python package
.. code:: bash
pip install ewoks
The script defines defines two tasks, one that ask for a name and the other that creates a greeting, creates a workflow out of these and executes it.
.. code:: python
from ewokscore import Task
from ewoks import execute_graph
# Define a workflow task with an output
class AskForName(Task, output_names=["input_name"]):
def run(self):
name = input("What is your name?")
if not name:
name = "World"
self.outputs.input_name = name
# Define a workflow task with inputs and outputs
class SayHello(
Task,
input_names=["name"],
optional_input_names=["in_french"],
output_names=["greeting"],
):
def run(self):
name = self.inputs.name
if self.inputs.in_french:
hello = "Bonjour"
else:
hello = "Hello"
self.outputs.greeting = f"{hello}, {name}!"
# Define nodes: entities that will execute tasks
nodes = [
{
"id": "ask_for_name",
"task_type": "class",
"task_identifier": "__main__.AskForName",
},
{
"id": "say_hello",
"task_type": "class",
"task_identifier": "__main__.SayHello",
},
]
# Define links that make data flow from one node to another
links = [
{
"source": "ask_for_name",
"target": "say_hello",
"data_mapping": [{"source_output": "input_name", "target_input": "name"}],
}
]
# Define a workflow from nodes, links and graph metadata
workflow = {"graph": {"id": "hello_world"}, "nodes": nodes, "links": links}
# Execute a workflow
result = execute_graph(workflow)
print(result)
print('----')
# Optionally, define inputs
inputs = [{"id": "say_hello", "name": "in_french", "value": True}]
# Execute a workflow with inputs
result = execute_graph(workflow, inputs=inputs)
print(result)
This is the output you should get
.. code-block:: bash
$ python hello_world.py
What is your name? Ewoks # <--- `input` waits for some input. `Ewoks` was typed here and Enter pressed.
{'greeting': 'Hello, Ewoks!'}
----
What is your name? # <--- Enter was pressed without typing anything
{'greeting': 'Bonjour, World!'}
To go further
-------------
- The `Ewoksfordevs training <https://ewoksfordevs.readthedocs.io/>`_ gives a more gentle introduction to workflow creation/execution as well as task creation.
- The `Ewoks website <https://ewoks.esrf.fr/en/latest/tutorials/>`_ also gathers more focused tutorials:
- `Workflow creation <https://ewoks.esrf.fr/en/latest/tutorials/create_workflow.html>`_
- Plus others to come!
- Ewoks developers rarely design workflows by hand like this but instead use graphical interfaces to produce the dictionnary (usually stored in JSON). See `this page about the Ewoks graphical interfaces <./howtoguides/gui>`_.
- For all the fields that can be set when creating the dictionnary representing the workflow, see the `Ewoks specification <https://ewokscore.readthedocs.io/en/latest/definitions.html>`_
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