Nothing takes the place of meaningful and substantive study, but these cheat sheets (that's really not a great term for them) are a handy reference in a pinch or for reinforcing particular ideas. All images link back to the cheat sheets in their original locations.

What you will find in here:

• Page 1 - Python Data Science Cheat Sheets
• Page 2 - R Data Science Cheat Sheets
• Page 3 - Probability, Algebra, Maths & SQL & Deep Learning Cheat Sheets

Python Data Science Stack

Python for Data Science (via DataCamp)

Pandas Basics (via DataCamp)

Pandas (via DataCamp)

Numpy (via DataCamp)

SciPy (via DataCamp)

Scikit-learn (via DataCamp)

Matplotlib (via DataCamp)

Bokeh (via DataCamp)