How can I use the safari selenium driver to get stored username and password?

Hi. I need to do some repetitive web tasks. These consists of downloading somewhat sensitive documents (sensitive to me) from a web server on a daily basis. I have a Python script using the selenium driver but I don't want the username and password stored as text. Instead I was hoping to use the encrypted username and password already stored in the keychain of the Safari browser. How can this be done?