So you want to login by SSH to your PythonAnywhere installation without using a password from your Mac?
First login to your PythonAnywhere account like so:
$ ssh <username>@ssh.pythonanywhere.com
NB: <username> is your PythonAnyhwre username. Not your email address. The password is the same password you use to login to the web site.
When logged in, create a .ssh folder in your home-folder like so:
Now logout, and create and create a SSH public/private key pair on your Mac like so:
$ ssh-keygen -t rsa -f name-of-your-key
Now, from your Mac run this command to append your public key to authorized_keys on the remote PythonAnywhere host:
$ cat ~/.ssh/name-of-your-key.pub | ssh <username>@ssh.pythonanywhere.com 'cat >> .ssh/authorized_keys'
Also create a config locally on your Mac in ~/.ssh/config:
Host PythonAnywhereName Hostname ssh.pythonanywhere.com Port 22 User <username> IdentityFile ~/.ssh/name-of-your-key
Now you can login like so:
$ ssh PythonAnywhereName