Python course / Working Python

Modules and imports

Split a program across files and packages, and know what import actually does. Two modules that need each other fail on import, and knowing why is the difference between a fix and a guess.

import forms
__name__
packages
relative imports
circular imports
pip
virtual environments
what goes where

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what a module is, from the inside

import json
import sys

print("name of this module:", __name__)
print("json came from:", json.__name__)
print("already imported:", "json" in sys.modules)

if __name__ == "__main__":
    print("this file was run, not imported")

name of this module: __main__
json came from: json
already imported: True
this file was run, not imported

What you will learn

Move code into a second file and use it from the first.
Choose how a name from another module arrives in yours.
Write a file that does its work when it is run and stays quiet when it is imported.
Group related modules into a folder and import them by a dotted name.
Find the module that already does it before writing it yourself.
Split a program into modules along the lines that change together.

The lessons in this module

What a module is
Three ways to import
What import actually does
Running once
Run, or imported
Where Python looks
Packages
Relative and absolute imports
Circular imports
The standard library
Packages from outside: pip
Virtual environments
What to put where
Work done on import
From one file to a package
Module review: the order desk

Ready when you are

Start this module

Previous: Classes and objects. Next: Comprehensions. All modules are on the course page.