I just wanted to share this site I discovered yesterday: Codewars
It's a collection with quite a few programming challenges, many of them supporting Python, and it seems to be quickly growing.
All the challenges are rated by difficulty from super-simple to fairly difficult, and can be filtered by difficulty and category.
From what I've seen, there are many challenges targeted for beginners, and a few fairly challenging ones.
I've enjoyed the site so far, I'm hoping someone will join the fun.