Installing and Using Python

Python is a widely used scripting language that emphasizes code readability and simplicity. It’s an excellent language for developing programs on the Omega, and it’s incredibly easy to get started.

Installing Python

The Omega supports Python, we recommend installing the light version to save on space.

The light version takes about 2.5MB of space on the Omega, whereas the full version is approximately 6.3MB.

Python 2.7

We are going to use opkg to install Python 2.7. Enter the following command to update your package manager:

opkg update

Now you can install python-light:

opkg install python-light

or the full version of python:

opkg install python

Python3

The light and full version of Python3 are also available via opkg. To install Python3, start by updating your package manager:

opkg update

Now you can install python3-light:

opkg install python3-light

or the full version of python3:

opkg install python3

Getting More Python Modules

There’s two ways to install additional Python modules on the Omega, either using opkg to install precompiled packages, or using pip, the Python package manager.

Using `opkg` to Install Python Modules

Once you’ve installed Python (or Python3), you can use opkg to install additional Python packages. This is probably the quicker method, but the selection of available packages is likely smaller than when using pip.

To see a list of the python packages available via opkg, enter the following commands:

opkg update
opkg list | grep python

Note: use opkg list | grep python3 to get the packages specific to Python3

This will list all the available packages with python in their name. You can run:

opkg install <PACKAGE NAME>

To install the desired package.

For more on opkg you can check out our guide to using opkg

For example, if you would like your script to make HTTP requests, you will need the urllib3 package:

opkg update
opkg install python-urllib3

And then your scripts can import the module:

import urllib3

Using `pip` to Install Python Modules

The official Python package manager, pip, is the standard way of installing Python modules on a system. You will get a large selection of available packages from which to choose.

Installing `pip`

We’ll need to first install pip on the Omega:

opkg update
opkg install python-pip

Note: use opkg install python3-pip to install pip for Python3

Installing Modules

To install a module:

pip install <module name>

Let’s say I’m writing a script that uses MQTT and would like to use the paho-mqtt module:

pip install paho-mqtt

Much like opkg, pip is a feature-complete package manager. Run pip --help to see more usage options or look up their documentation.

Fixing “No space left on device”

If you’re trying to install a Python module with pip and get an error like the following:

root@Omega-C71D:/# pip3 install boto3
Collecting boto3
...
Collecting botocore<1.25.0,>=1.24.13 (from boto3)
  Downloading https://files.pythonhosted.org/packages/a5/34/567e87ece4328f51a6db92db8c58584aa9525603c86aff5eb77bfc713b41/botocore-1.24.13-py3-none-any.whl (8.6MB)
    100% |████████████████████████████████| 8.6MB 262kB/s 
Could not install packages due to an EnvironmentError: [Errno 28] No space left on device

This is due to pip using the /tmp directory for work by default. The tmpfs /tmp directory is too small for very large packages. This can be overridden with the TMPDIR environment variable. It is recommended to boot from external storage.

mkdir /root/temp
export TMPDIR=/root/temp
pip3 install <large_package>

Fixing the Setup Tools Issue

If you’re trying to install a Python module with pip and get an error like the following:

root@Omega-296A:~# pip install paho-mqtt
Collecting paho-mqtt
  Downloading paho-mqtt-1.2.tar.gz (49kB)
    100% |████████████████████████████████| 51kB 215kB/s
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-cHKrSf/paho-mqtt/

Don’t worry! It’s just a small configuration issue with the setuptools module and cab be easily fixed with the following command:

pip install --upgrade setuptools

Now you’ll be able to successfully use pip:

root@Omega-296A:~# pip install --upgrade setuptools
Collecting setuptools
  Downloading setuptools-34.2.0-py2.py3-none-any.whl (389kB)
    100% |████████████████████████████████| 399kB 109kB/s
Collecting appdirs>=1.4.0 (from setuptools)
  Downloading appdirs-1.4.0-py2.py3-none-any.whl
Collecting packaging>=16.8 (from setuptools)
  Downloading packaging-16.8-py2.py3-none-any.whl
Collecting six>=1.6.0 (from setuptools)
  Downloading six-1.10.0-py2.py3-none-any.whl
Collecting pyparsing (from packaging>=16.8->setuptools)
  Downloading pyparsing-2.1.10-py2.py3-none-any.whl (56kB)
    100% |████████████████████████████████| 61kB 343kB/s
Installing collected packages: appdirs, pyparsing, six, packaging, setuptools
Successfully installed appdirs-1.4.0 packaging-16.8 pyparsing-2.1.10 setuptools-34.2.0 six-1.10.0
root@Omega-296A:~# pip install paho-mqtt
Collecting paho-mqtt
  Using cached paho-mqtt-1.2.tar.gz
Installing collected packages: paho-mqtt
  Running setup.py install for paho-mqtt ... done
Successfully installed paho-mqtt-1.2

Using Python

Since the Omega is a Linux computer, it’s really easy to get started with Python on the Omega. You can enter python in your command-line to start the interpreter.

If you’ve installed Python3, you’ll need to enter python3 in your command-line to get started.

Note that the interpreter is a good tool for quickly testing some code, but the real power of Python comes from writing reusable scripts.

Writing a Python Script on the Omega

Let’s begin writing our Python script by creating the file:

vi /root/greeting.py

Now we’ll copy the following code into the file:

# Importing packages
import os, datetime, time, subprocess

# find the path to the Omega LED
ledName = subprocess.check_output(["uci", "get", "system.@led[0].sysfs"])
ledTriggerPath = "/sys/class/leds/%s/trigger"%(ledName.rstrip())

## Set the Omega LED trigger to "timer" so that it blinks
with open(ledTriggerPath, "w") as trigger:
          trigger.write("timer")


## Print a gretting based on the time of day
# Gets the current time
currentTime = datetime.datetime.now()

# Sets the Omega LED trigger to "default-on"
if currentTime.hour < 12:
        print 'Good morning.'
elif 12 <= currentTime.hour < 18:
        print 'Good afternoon.'
else:
        print 'Good evening.'


## Wait 5 seconds and then set the Omega LED back to being always on
# Waits for 5 seconds
time.sleep(5)

# Set the Omega LED back to being always on
with open(ledTriggerPath, "w") as trigger:
        trigger.write("default-on")

To save and exit your file, hit ESC and then enter :wq.

You can execute the script using the following command:

python /root/greeting.py

Note: If you installed Python3, you would enter python3 instead of python.

And you’ll see the following output:

root@Omega-2757:~# python /root/greeting.py
Good evening.

During this time your Omega’s LED will be blinking on and off.

Onion Python Modules

We’ve developed modules for controlling the Omega’s GPIOs and several Expansions. Check out the documentation for the Modules for more details:

Going Further

This section will give you more information on how you can use Python on the Omega to create fantastic projects.

Learning Python

Python 2.7 documentation
Python 3 documentation