Python Modules

A module is a Python file. A package is a folder of modules. import pulls one in.

Import forms

import math
print(math.pi)

from math import pi, sqrt
print(sqrt(2))

import numpy as np      # aliased
from collections import (
    Counter, defaultdict, OrderedDict,   # bracketed grouped imports
)

Your own module

Make a file shapes.py:

PI = 3.14159

def area(r):
    return PI * r * r

Then in another file in the same folder:

import shapes
print(shapes.area(5))

Packages

A folder becomes a package if it contains __init__.py (empty is fine). Sub-folders become sub-packages:

shop/
  __init__.py
  customers.py
  orders/
    __init__.py
    items.py

from shop.orders.items import format_total

Where Python looks

Python searches in order:

1. The directory of the running script.
2. Directories in PYTHONPATH.
3. The standard library.
4. Installed packages (site-packages).

Example

import math
import json
print(math.pi, math.sqrt(16))
print(json.dumps({'ok': True}))

Exercise

Test yourself