how can I find out which python virtual environment I am using?

From a shell prompt, you can just do echo $VIRTUAL_ENV (or in Windows cmd.exe, echo %VIRTUAL_ENV%).

From within Python, sys.prefix provides the root of your Python installation (the virtual environment if active), and sys.executable tells you which Python executable is running your script.

Usually it's set to display in your prompt. You can also try typing in which python or which pip in your terminal to see if it points to you venv location, and which one. (Use where instead of which on Windows.)

You can use sys.prefix to determine which virtualenv you're in.

import sys
print(sys.prefix)

from the sys docs

A string giving the site-specific directory prefix where the platform independent Python files are installed