For a lightweight Python application that needs to run continuously and securely on a free server, you have a few options:
1. Cloud Platforms
GitHub Codespaces: GitHub Codespaces provides a cloud-based development environment where you can run code. It might be suitable for your needs if the resource limits are sufficient.
Repl.it: Repl.it offers a free tier that allows you to run Python code continuously. It also has built-in version control and a secure environment.
Glitch: Glitch offers free hosting for small projects. It’s ideal for low-computation tasks and provides a secure environment.