Python Import: Modules, from…import and as
A module is a file of Python code you can reuse. The import statement loads one, so you can use its functions, such as math.sqrt().
Python comes with hundreds of modules, called the standard library. Read Defining functions first.
Import a module
Write import and the module name at the top of your file. Then put the
module name and a dot before each thing you use from it.
import math
print(math.sqrt(16))
print(math.pi)
print(math.floor(7.9))
math.sqrt is the sqrt function inside the math module. The dot keeps
it apart from any sqrt of your own.
Import only some names with from…import
from math import sqrt, pi brings in just those names. You then use them
without math. in front.
from math import sqrt, pi
print(sqrt(25))
print(round(pi, 2))
Give a module a shorter name with as
as renames what you import. It saves typing for long module names.
import statistics as stats
scores = [3, 10, 5]
print(stats.mean(scores))
print(stats.median(scores))
stats now means the statistics module. Some libraries have a short name
everyone uses, such as import numpy as np.
When an import fails
The name must match the module exactly. A typo stops the program.
import maths # this line raises ModuleNotFoundError
The module is math, not maths. Packages from outside the standard
library, such as numpy, need pip install on your own computer first.
Note: Avoid from math import *. It brings in every name at once, so
you can no longer tell where a name came from. It can also replace names
you made yourself.
See also: Create your own module, Regex basics.
Your turn
Import mean and median from statistics. Print both for scores on one
line.
scores = [2, 9, 4]
# add two lines: import mean and median from statistics, then print both
Expected output
5 4