Why does my Python app fail to deploy?

When you build a Python app from source, the image builds and is visible in Container Registry. However, the app fails to deploy.

When you build Python from a buildpack, the buildpack does not provide a way to define a start process. By default, it sets the start process to python, which starts the correct version's REPL. To run a Python program, the Procfile mechanism can be used to override the default start process: web.

The following Procfile sets the entrypoint of the resulting image to main.py and must be present in the root of the context directory.

web: python main.py