Automated acces to website data that is password protected [closed]

I'm a group admin of a social network. For our anniversary I'd like to do some statistics, who is in our group. This is anonymous but consent is granted :)
The data science stuff I know but I'm a total networking and web noob.
So what I need is a script that visits a website (Let's assume no API) and gets the content of the page. I guess I can use regex to get the keywords I want. But I really have no idea how such a ping and cache website script works. But the catch is as with any social network the website requires a login. I mean I have credentials but I assume it's much harder to write such a script for login blocked websites.
So any guidance is very much appreciated. A Python solution would be the best, but if there is another solution that I can use as a black box and then do my data science with python this is fine too. Many thanks for your help :)