Home automation with Home Assistant on Raspberry PI – Getting Started

Hi ๐Ÿ‘‹

The purpose of this article is to get you started quickly with a Home Assistant on a Raspberry Pi. It’s a simple walkthrough on how to install Home Assistant and configure it so it will boot with your PI.

I will use my old Raspberry PI V3 board.

Flashing the Raspberry PI OS

You will need a microSD card of reasonable size, I’m using a 16GB one and a USB Adapter to connect it with my PC.

Head over to Raspberry Pi OS website and download your preferred image, for my Home Assistant I’ve chosen Raspberry Pi OS with desktop and recommended software. After the download is completed, unzip the file and prepare to flash it.

To flash the OS image on the SD card I will use a program called balenaEtcher.

Download it, select your OS image, select the SD card, and hit flash.

After SD card flashing finishes, it is time to setup the Wi-Fi connection. If you’re using an ethernet cable you can skip this step, however, remember to enable SSH.

Setting up the Wi-Fi and enabling SSH

Unplug the SD card from the computer and plug it back. You should see two new drives D: and E:

  1. Open your favorite text editor and create an empty file called ssh in drive E:. This will enable SSH access.
  2. Create a new file called wpa_supplicant.conf using your text editor and paste the following contents in it:
country=us
update_config=1
ctrl_interface=/var/run/wpa_supplicant

network={
   scan_ssid=1
   ssid="YOUR_WIFI_SSID"
   psk="YOUR_WIFI_PASSWORD"
}

Don’t forget to replace YOUR_WIFI_SSID and YOUR_WIFI_PASSWORD with the corresponding values regarding your Wi-Fi network.

Eject the SD card from your computer and plug it into the PI. At boot, the PI should automatically connect to your Wi-Fi network.

Installing Home Assistant Core

Find your Raspberry PI’s IP address and connect to it via ssh. You can run the command ssh pi@192.168.0.XXX. The password for the pi user should be raspberry.

After getting a shell, follow the instructions for installing Home Assistant from the official website.

Ensure that you run each command on its own line. Don’t directly copy the entire code block, copy each line individually.

Starting Home Assistant on boot

If you can access the Home Assistant web GUI using http://192.168.0.XXX:8123 then the next step would be to create a new systemd service so that some assistant starts at boot. Please replace XXX with your Raspberry PI’s IP address.

To create a new service:

  1. Start a new shell on the Raspberry or ensure that you’re using the pi user. We will execute commands with sudo.
  2. Use sudo nano /etc/systemd/system/hass.service to create a new file and paste the following contents into it:
[Unit]
Description=HomeAssistant Service
After=network.target

[Service]
User=homeassistant
WorkingDirectory=/home/homeassistant
Environment="PATH=$PATH:/srv/homeassistant/bin"
ExecStart=/srv/homeassistant/bin/hass

[Install]
WantedBy=multi-user.target

Stop hass command if it’s running and enables the service by executing:

sudo systemctl start hass.service
sudo systemctl enable hass.service
sudo systemctl status hass.service

If the service is running normally, everything is set up. You can safely reboot your PI and the Home Assistant service will run after boot.

Configuring Home Assistant

When visiting the Home Assistant’s web interface for the first time, you will be prompted to create a new user. You may also download the Home Assistant application for your mobile device if you wish to track things like battery, storage, steps, location and so on, in Home Assistant.

In future articles I will show you how to configure the BME680 enviromental sensor and how to activate the Apple Homekit integration. Until then, have fun exploring Home Assistant docs.

Things to do further:

Unattended Upgrades – Enable unattended upgrades for your Raspbian OS. Ensures that your OS’s is always patched and up to date.

UFW – Secure your Home Assistant server with the uncomplicated firewall.

Change default passwords or disable SSH login via password.

Thanks for reading and happy automations! ๐Ÿ“š

Pytest Fixtures and Yield

Hi ๐Ÿ‘‹

In this short article I want to explain the use of the yield keyword in pytest fixtures.

What is pytest?

Pytest is a complex python framework used for writing tests. It has lots of advanced features and it supports plugins. Many projects prefer pytest in addition to Python’s unitttest library.

What is a fixture?

A test fixture is a piece of code that fixes some common functionality that is required for writing the unit tests. This functionality can be

  • a connection to the database
  • a testing http server or client
  • creation of a complex object

You can read more about test fixtures on Wikipedia.

What does yield keyword do?

In Python, the yield keyword is used for writing generator functions, in pytest, the yield can be used to finalize (clean-up) after the fixture code is executed. Pytest’s documentation states the following.

โ€œYieldโ€ fixtures yield instead of return. With these fixtures, we can run some code and pass an object back to the requesting fixture/test, just like with the other fixtures.

https://docs.pytest.org/en/6.2.x/fixture.html

An example code could be the following:

@pytest.fixture()
def my_object_fixture():
    print("1. fixture code.")
    yield MyObjectThatRequiresCleanUp()
    print("4. fixture code after yield.")

Running a sample test which utilizes the fixture will output:

collected 1 item                                                                                                                                                                       

tests\test_my_object.py 1. fixture code.
2. Initializing MyObjectThatRequiresCleanUp
3. test code.
.4. fixture code after yield.

Running the same test but now with the fixture my_object_fixture2, will output:

tests\test_my_object.py 1. fixture code.
2. Initializing MyObjectThatRequiresCleanUp
2.1 Entering
3. test code.
.3.1 Exiting
Clean exit
4. fixture code after yield.

I hope I could successfully ilustrate with these examples the order in which the testing and fixture code is run.

To run the tests, I’ve used pytest --capture=tee-sys . in the project root. The file contents are attached to the end of this article. The --capture parameter is used to capture and print the tests stdout. Pytest will only output stdout of failed tests and since our example test always passes this parameter was required.

Conclusion

Pytest is a python testing framework that contains lots of features and scales well with large projects.

Test fixtures is a piece of code for fixing the test environment, for example a database connection or an object that requires a specific set of parameters when built. Instead of duplicating code, fixing the object’s creation into a fixture makes the tests easier to maintain and write.

yield is a python keyword and when it is used in conjunction with pytest fixtures it gives you a nice pythonic way of cleaning up the fixtures.

Thanks for reading! ๐Ÿ“š


Contents of the Pytest fixtures placed in tests/__init__.py

import pytest

from my_object import MyObjectThatRequiresCleanUp


@pytest.fixture()
def my_object_fixture():
    print("1. fixture code.")
    yield MyObjectThatRequiresCleanUp()
    print("4. fixture code after yield.")


@pytest.fixture()
def my_object_fixture2():
    print("1. fixture code.")
    with MyObjectThatRequiresCleanUp() as obj:
        yield obj
    print("4. fixture code after yield.")

Contents of my_object.py

class MyObjectThatRequiresCleanUp:
    def __init__(self):
        print("2. Initializing MyObjectThatRequiresCleanUp")

    def __enter__(self):
        print("2.1 Entering")
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        print("3.1 Exiting")
        if exc_type is None:
            print("Clean exit")
        else:
            print("Exception occurred: {}".format(exc_type))

Contents of test_my_object.py placed in tests/test_my_object.py

from tests import my_object_fixture


def test_my_object(my_object_fixture):
    print("3. test code.")