I have been getting questions on this, so here is a compilation of free/affordable resources you can try to learn Python online from, within the context of Data Science:
Udemy
Complete Python Bootcamp: Go from zero to hero in Python
Jose Portilla
Buy it when it is on offer and it should cost only $15SGD. You can claim this from Skillsfuture if you are Singaporean!
Python for Data Science and Machine Learning Bootcamp
Jose Portilla
same as above
Machine Learning A-Z™: Hands-On Python & R In Data Science
Kirill Eremenko, Hadelin de Ponteves
Haven’t tried this personally but heard good review from a friend - also $15/$18 when on offer
Datacamp
Kaggle Python Tutorial on Machine Learning
https://www.datacamp.com/community/open-courses/kaggle-python-tutorial-on-machine-learning
There are just a few free courses on Datacamp, feel free to explore, but this was pretty fun
Udacity
https://www.udacity.com/courses/all
I am still in the midst of figuring this out, but apparently if you go into the individual courses some of them are free, even though they are part of the nanodegree (which as a whole is not free)
Dataquest
Haven’t tried this personally, but seems like there are some basic courses for free as well according to a friend
Coursera
Also still trying to figure this out, but apparently materials are free. You only pay for graded assignments and certification
Codecademy
For basics
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For the guys who have learnt and want to test your skills, I’d suggest giving the below a try. Practice makes perfect!
Project Euler
Reddit Daily Programmer
https://www.reddit.com/r/dailyprogrammer/
Kaggle
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For those who want to make your code more Pythonic:
https://gist.github.com/JeffPaine/6213790
http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html
https://www.python.org/dev/peps/pep-0257/ (specific to docstrings)