IDAPython requires a Python3.x installation in order to work. Because different users might have different (and possibly multiple) versions of Python3.x installed, IDA comes with a tool called `idapyswitch` that can be run to select the desired Python3.x runtime. If you selected IDAPython-for-Python3.x at the installation time, the `idapyswitch` utility should already have been run and selected the most appropriate Python3.x version. Should you want to switch to another Python3.x install after installation, please run `idapyswitch` from the IDA directory. It will scan for Python installs present in the system's standard locations and offer you to choose one. It also supports optional command-line switches to handle non-standard installs. Run `idapyswitch -h` to see them.