What is a cheat sheet?

As the name indicates, cheat sheets present the fundamental elements of a programming language or even a programming library. There are important and basic and they are commonly used, and even if you'll probably finish by learning them, it is always interesting to be able to take a look at them.

There are more complete cheat sheets, but I am going to leave you the most basic cheat elements for a few common programming languages below:

Python Cheat Sheet

Pandas Cheat Sheet

Keras Cheat Sheet

Pandas Cheat Sheet

Sklearn Cheat Sheet

Source: Data Science App

Where to find more complete cheat sheets?

It is as simple as google cheat sheets and the library or language of interest, BUT, I highly recommend you to visit Cheatography. 

Cheatography is an excellent tool to access cheatsheets, that have been created to help the programmer. It is divided by topics and has a forum section above other advantages.

Hope this will be helpful for you!