Modules

# You can import modules
import math
print(math.sqrt(16) )#=> 4

# You can get specific functions from a module
from math import ceil, floor
print(ceil(3.7))  #=> 4.0
print(floor(3.7)) #=> 3.0

# You can import all functions from a module.
# Warning: this is not recommended
from math import *

# You can shorten module names
import math as m
math.sqrt(16) == m.sqrt(16) #=> True

# `dir` lists all the functions and attributes defined by a module
import math
dir(math)
# => [... 'acos', 'acosh', 'asin', 'asinh', 'atan'] #and more...

Create your own modules

Python modules are just ordinary python files. You can write your own, and import them. The name of the module is the same as the name of the file.

greetings.py file:

def say_hi():
  print("Hi")

def say_bye():
  print("Bye")

Console:

import greetings
greetings.say_hi() # => Hi
greetings.say_bye() # => Bye