Which online training sites have good content?
Paid online training can provide a more structured approach to learning. I have found it most useful to start with some paid online training courses and then supplement or fill in the blanks with free online tutorials. I have found the following sites useful:
Lynda is a monthly subscription service with lots of high-quality training courses covering many subjects. This can be very useful because inevitably you will find that to use Python effectively you will also need to know at least some basics of Linux, Git, Web protocols, DBs etc. Lynda also allows you to download the courses to watch offline which can be very useful if you travel.
Udemy also has a great selection of high-quality training courses that can be purchased individually without a subscription.