Individual course certs were about $50 which adds up for a multi-class sequence. Courses are generally free to register and take and they only charge if you want the printed cert to show off.
https://www.coursera.org/specializations/investment-management-python-machine-learning might be what you're looking for. Specializations can get pricey quick but it's cheaper than an graduate degree.
You could also look at kaggle.com for practice. Work in R and then try to duplicate it in Python. I like codewars.com too. It's a gamefied platform for problem solving that supports many languages.