git-flask-python : Is it safe to remove pycache and flask session folders

Both these folders contain temporary objects that are created in runtime, and there's no point in committing them to git. I'd remove those folders from your repository and then add them to .gitignore to prevent them from being re-added there by mistake.

If you look at gitignore.io/python, you will find in the generated .gitignore file

### Python ###
# Byte-compiled / optimized / DLL files
__pycache__/

However, you won't find flask_session, not even in flask-common/.gitignore.

The Flask documentation mentions:

SESSION_FILE_DIR The directory where session files are stored.
Default to use flask_session directory under current working directory.

If that is something private to the user and the flask execution, then add to your .gitignore:

/*_session/

But considering a Flask session stores secrets, the best practice would be to configure Flask to store its session outside the Git repository: that way, no risk to add by mistake anything, .gitignore or not.

In layman language, YES because these things can be generated again by Flask thus it's good practise to not push it to a repo and generate locally individually.