Why is the ['...'] in Python?

I showed the data on the prompt as I wanted. I took the pdf link as a regular expression, but I think it's in the string format.

The problem is ['........................'] I want to remove it, but I can't.

Maybe it's because I put the string on automatically, so I'm thinking about it by myself.

I'd like to leave only http://..........pdf neatly.

Please tell me.