Modules

Two different notations
When you need lots of functions from the library and want to be explicit

import math 

print(math.sqrt(16))

When you only need 1 or 2 specific functions and do not want to prefix them

from math import sqrt 

print(sqrt(16))

You can also give the library an alias name for shorter prefixing import module_name as alias_name

import math as math_aliasname 

print(math_aliasname.sqrt(16))