You can get started with something simple as this:
from piston.steem import Post, Steem
post = Post(Steem(), "@xeroc/piston")
post.reply("Title", "body", author="YOURACCOUNT")
Or you go through piston using the command line tool:
piston read @xeroc/piston-cli-quickstart
RE: [piston.web] First Open Source Steem GUI - Searching for alpha testers