So far i've got fairly far with pythonchallenge and it's been good fun discovering all these modules and aspects of python i didn't previously know about.
Most of what I do in python or indeed any language is just to solve equations and so it's been particularly fun just learning a language like this.
Another website which was good was https://Check.io . There is an interactive world in which you use Python to solve challenges and go further in life. With active members on the forums to direct you whenever you are lost means no step is too big.
Further along, another website is https://trinket.io which allows you to share snippets of running python (only with standard libraries). You can share them as code and program, or quite simply just program. A nice tool for learning how to code in python without having to mess with the terminal or an IDE.