If you run brew info python it will show something akin to:
Unversioned symlinks `python`, `python-config`, `pip` etc. pointing to
`python3`, `python3-config`, `pip3` etc., respectively, have been installed into
/usr/local/opt/python@3.9/libexec/bin
So adding /usr/local/opt/python@3.9/libexec/bin to your PATH will allow for python calls to work.