Data Science is a very broad field and may cover difference techniques in difference companies/circumstances. From your hashtags I am assuming you wanted to learning Machine Learning.
Nowadays there are many useful beginner ML classes online you can find. The most famous one is the one from Andrew Ng on Coursera https://www.coursera.org/learn/machine-learning. It covers the basic of ML.
After getting basic ideas, you can start playing with different Python package on public datasets. You can check out Kaggle competitions, find simple problems to solve, and see how other people solve it in the Kaggle forum. Learning by doing is the way I found most effective. :)
Sean recommends the following next steps:
- Take https://www.coursera.org/learn/machine-learning
- Play with public datasets