Python Interpreter examples¶
Here you can see how we load and execute Python scripts inside a Sen process.
First make sure that you have the PYTHONPATH environment variable correctly set to point to our
example scripts:
For bash:
For fish:
Hello Python¶
In this example we just show how to get a Python interpreter running inside a Sen component.
Run it with:
hello_python.py
# === hello_python.py ==================================================================================================
# Sen Infrastructure
# Released under the Apache License v2.0 (SPDX-License-Identifier Apache-2.0).
# See the LICENSE.txt file for more information.
# © Airbus SAS, Airbus Helicopters, and Airbus Defence and Space SAU/GmbH/SAS.
# ======================================================================================================================
import sen
# this is executed only once (at the start of the component execution)
def run():
print(f"Python: run")
print(f"Python: the config is: {sen.api.config}")
print(f"Python: the app name is: {sen.api.appName}")
# this is executed every cycle
def update():
print(f"Python: update (current time: {sen.api.time})")
# this is executed only once (at the end of the component execution)
def stop():
print(f"Python: stop called")
Inspecting objects¶
In this example we can see how to fetch objects coming from other components and print their properties.
Run it with:
This example contains the following files:
inspecting_objects.py
# === inspecting_objects.py ============================================================================================
# Sen Infrastructure
# Released under the Apache License v2.0 (SPDX-License-Identifier Apache-2.0).
# See the LICENSE.txt file for more information.
# © Airbus SAS, Airbus Helicopters, and Airbus Defence and Space SAU/GmbH/SAS.
# ======================================================================================================================
import sen
# to store the objects that we want to inspect
list = None
def run():
global list # refer to the global variable defined above
list = sen.api.open("SELECT * FROM local.kernel") # open it
# register some callbacks to show changes in the list
list.onAdded(lambda obj: print(f'Python: object added {obj}'))
list.onRemoved(lambda obj: print(f'Python: object removed {obj}'))
def update():
# refer to the global variable defined above
global list
print(f"Python: printing the list at: {sen.api.time})")
print(list)
print("Python: iterating over the objects in the list:")
for obj in list:
print(f"Python: * object {obj.name}")
print(f"Python: - class: {obj.className}")
print(f"Python: - id: {obj.id}")
print(f"Python: - time: {obj.lastCommitTime}")
Creating objects¶
In this example we ee how to create and publish objects using Python.
Run it with:
This example contains the following files:
creating_objects.py
# === creating_objects.py ==============================================================================================
# Sen Infrastructure
# Released under the Apache License v2.0 (SPDX-License-Identifier Apache-2.0).
# See the LICENSE.txt file for more information.
# © Airbus SAS, Airbus Helicopters, and Airbus Defence and Space SAU/GmbH/SAS.
# ======================================================================================================================
import sen
myObject = testBus = None
def run():
global myObject, testBus # refer to the globals defined above
type = {
"entityKind": 1,
"domain": 2,
"countryCode": 198,
"category": 1,
"subcategory": 3,
"specific": 0,
"extra": 0
}
id = {
"entityNumber": 1,
"federateIdentifier": {
"siteID": 1,
"applicationID": 1
}
}
print(f"Python: creating and publishing the object")
myObject = sen.api.make("aircrafts.DummyAircraft", "myAircraft", entityType=type, alternateEntityType=type, entityIdentifier = id)
testBus = sen.api.getBus("my.tutorial")
testBus.add(myObject)
def update():
print(myObject)
def stop():
global testBus, myObject # refer to the globals defined above
print("Python: deleting the object")
testBus.remove(myObject)
myObject = None
testBus = None
Interacting with objects¶
Here we can see how to call methods on objects coming from other components.
Run it with:
This example contains the following files:
interacting_with_objects.py
# === interacting_with_objects.py ======================================================================================
# Sen Infrastructure
# Released under the Apache License v2.0 (SPDX-License-Identifier Apache-2.0).
# See the LICENSE.txt file for more information.
# © Airbus SAS, Airbus Helicopters, and Airbus Defence and Space SAU/GmbH/SAS.
# ======================================================================================================================
import sen
# to store the object
obj = None
def run():
global obj # refer to the global variable defined above
obj = sen.api.open("SELECT * FROM local.shell WHERE name = \"shell_impl\"")
def update():
global obj # refer to the global variable defined above
print("Python: update")
# if the object is present, do something with it
if len(obj) != 0:
print("Python: interacting with the object")
obj[0].info("i16") # print the info of the i16 type
obj[0].ls() # list the current objects in the terminal
obj[0].history() # show the current history
print("Python: asking the process to shut down")
obj[0].shutdown() # trigger the process shutdown
Reacting to events and changes¶
Here we can see how to execute Python code when events are produced or properties change.
It relies on the "school" example to get some activity going.
Run it with:
This example contains the following files:
reacting_to_events_and_changes.py
# === reacting_to_events_and_changes.py ================================================================================
# Sen Infrastructure
# Released under the Apache License v2.0 (SPDX-License-Identifier Apache-2.0).
# See the LICENSE.txt file for more information.
# © Airbus SAS, Airbus Helicopters, and Airbus Defence and Space SAU/GmbH/SAS.
# ======================================================================================================================
import sen
# to store the objects
teachers = None
def teacherDetected(teacher):
teacher.onStressLevelPeaked(lambda args: print(f"Python: {teacher.name} stress level peaking to {args}"))
teacher.onStatusChanged(lambda: print(f"Python: {teacher.name} status changed to {teacher.status}"))
def run():
global teachers # refer to the global variable defined above
print("Python: run")
# select the object and install some callbacks
teachers = sen.api.open("SELECT school.Teacher FROM school.primary")
teachers.onAdded(lambda obj: teacherDetected(obj))
Using the interpreter from other components¶
Here we publish the interpreter object and can use it from within our shell component.
This example contains the following files:
6_python_interpreter.yaml
# $schema: ../base/schema.json
include:
- ../base/shell.yaml
load:
- name: shell
open: [local.py]
- name: py
group: 3
freqHz: 30
bus: local.py
If you open the shell you can use the interpreter with something like this:
The eval function evaluates an expression and returns the result.
The exec function executes statements.
The interpreter holds an internal state, so you can use it in your evaluations.