Create a file named your-service.service and include the following:
[Unit]
Description=<description about this service>
[Service]
User=<user e.g. root>
WorkingDirectory=<directory_of_script e.g. /root>
ExecStart=<script which needs to be executed>
Restart=always
[Install]
WantedBy=multi-user.target
Example
[Unit]
Description=<project description>
[Service]
User=<user e.g. root>
WorkingDirectory=<path to your project directory>
ExecStart=/bin/bash -c 'cd /home/ubuntu/project/ && source venv/bin/activate && python test.py'
[Install]
WantedBy=multi-user.target
Reload the service files to include the new service.
sudo systemctl daemon-reload