Advanced Python import Techniques (Summary)

Advanced Python import Techniques Christopher Trudeau 04:16

In this video course, you’ve gotten to know the Python import system. Like many things in Python, it’s fairly straightforward to use for basic tasks like importing modules and packages. At the same time, the import system is quite complex, flexible, and extendable. You’ve learned several import-related tricks that you can take advantage of in your own code.

In this video course, you’ve learned how to:

Create namespace packages
Import resources and data files
Decide what to import dynamically at runtime
Extend Python’s import system
Handle different versions of packages

Throughout the video course, you’ve seen many links to further info. The most authoritative source on the Python import system is the official documentation:

You can put your knowledge of Python imports to use by following along with the examples in this video course. Click the link below for access to the source code:

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Congratulations, you made it to the end of the course! What’s your #1 takeaway or favorite thing you learned? How are you going to put your newfound skills to use? Leave a comment in the discussion section and let us know.

00:00 In the previous lesson, I showed you several import tips and tricks. This is the final lesson. I’m going to summarize the course and point you at some more resources.

00:10 This course has been all about importing modules and packages into your Python programs. Modules and packages are ways of organizing your code and with apologies to Steven Wright you can’t have everything in your namespace.

00:22 Where would you put it? The namespace is where all references live, and you use the import keyword to bring external things into the namespace, including modules or objects inside those modules. A module corresponds to a single file, and if you want more structure than that, you use a directory.

00:40 By putting a __init__.py file in a directory, you are creating a package. That __init__.py file is still a Python file, so you can use it to write side effect code, including importing other things into the namespace.

00:54 You can replace an object in the namespace by bringing in other ones with the same name or creating variables that overload the name. When you do this, you shadow the original value.

01:05 If you shadow a built-in, you can recover it by deleting the redefined value.

01:10 Shadowing also affects module loading. If you have a module with the same name as a built-in one, most of the time your module shadows the original. There are cases though, where this doesn’t happen depending on how the thing being shadowed is defined.

01:24 Once you’ve got a package, you can bundle it up for re-use. To do so, you typically create a source directory for your code then add a pyproject.toml file to describe your bundle.

01:35 These kinds of bundles are what gets put up on PyPI, but you can use your own locally by installing it with the -e option to pip install.

01:45 An absolute import is one with a fully qualified name. You can also import things relative to the current file. This is typically done with the dot shortcut.

01:55 Relative imports aren’t recommended though. If you move your file, the import breaks. It also won’t work if you package up your code in an installable bundle or put it in a Python zip archive.

02:06 When you first import a module, Python caches it in the sys.modules dictionary. Subsequent loads use the cache version, including if you’ve changed the file.