1. Learn python 3 the hard way (book by Zed Shaw) as mentioned by trcarney)
2. Build a saas app with flask (Nick Janetakis, on Udemy or his own site)
Use these resources to look up things and get more context:
- real python
- stack overflow
After finishing #2, try to build a different saas project from scratch, using what you learned.
If your interest is ML/DS, then replace #2 with something like 'deep learning for coders' parts 1 and 2. Or work through pandas exercises.