Python comes with a huge standard library: hundreds of modules covering maths, dates, randomness, files, the internet, data formats and more. People say Python comes "with batteries included". Before writing something fiddly yourself, it's worth asking whether the standard library already does it.

There are three ways to import:

import math
print(math.sqrt(16))

from math import pi, floor
print(pi, floor(2.7))

import statistics as stats
print(stats.mean([2, 4, 9]))

import math brings in the module; you use its contents with math. in front. This is the clearest, because every use says where it came from.
from math import pi brings in just those names, usable without a prefix.
import ... as gives a module a shorter name.

Avoid from math import *, which brings in everything and makes it hard to tell where names came from.