How do I use modules

Question

There are alot of modules in python how do i know them do i need to remember some of them I mean what are the most important modules

Answer 1

Well os is important, it offers methods for accessing things such as command prompt.

Answer 2

I've needed:
os (for file handling, you can for example check which files exist in the current directory.
math (for trigonometric functions, pi and sqrt)
random (to add randomized functionality)
timeit (to compare speed of different pieces of code)
pygame (to handle graphics, controls and audio)