Further Reading: Modules, Packages, and the Python Ecosystem

Python Standard Library

Python Standard Library Documentation. (Tier 1) The official reference for every module in the standard library. Bookmark it: https://docs.python.org/3/library/. You don't need to read it cover to cover — use it as a reference when you need a specific module. The "Library and Extension FAQ" section is particularly useful for beginners.
Hellmann, D. Python 3 Module of the Week (PyMOTW-3). (Tier 1) An extensive collection of tutorials for standard library modules, with clear examples and explanations. More approachable than the official docs for learning new modules. Available free online at pymotw.com.

Python Packaging User Guide. (Tier 1) The official guide to installing, creating, and distributing Python packages. Covers pip, virtual environments, setup.py, pyproject.toml, and everything you need to publish your own package to PyPI. https://packaging.python.org/
Batchelder, N. (2017). "Packaging is Hard." PyCon Talk. (Tier 2) A clear-eyed talk about why Python packaging is confusing and what the community is doing about it. Helps contextualize the tools you'll encounter (pip, setuptools, wheel, etc.) and why there seem to be so many ways to do the same thing.

Martin, R. C. (2008). Clean Code: A Handbook of Agile Software Craftsmanship. Prentice Hall. Chapters 2-3 (Meaningful Names, Functions). (Tier 1) The classic reference on writing maintainable code. The chapters on naming and function design directly reinforce why module organization matters. Written with Java examples, but the principles are language-agnostic.
Raymond, E. S. (2003). The Art of Unix Programming. Chapter 4: Modularity. (Tier 1) A deep discussion of modularity as a design principle, drawing from decades of Unix software design. Covers the ideas behind why we split code into small, focused units. Available free online.

Python Package Index (PyPI). (Tier 1) The central repository for third-party Python packages: https://pypi.org/. Over 500,000 packages are available. Every pip install pulls from here.
Ziadé, T. (2008). Expert Python Programming. Packt. Chapter on Packaging. (Tier 2) A more advanced treatment of Python packaging, project structure, and distribution. Good for when you're ready to create your own installable package.

Fogel, K. (2005, updated). Producing Open Source Software. O'Reilly. (Tier 1) A comprehensive guide to how open source projects work — licensing, community management, contribution guidelines, and governance. Available free online at producingoss.com. Relevant context for understanding the ecosystem you're tapping into with pip install.
Eghbal, N. (2020). Working in Public: The Making and Maintenance of Open Source Software. Stripe Press. (Tier 1) An insightful look at the economics and social dynamics of open source software. Explores why people maintain packages for free, the "maintainer burnout" problem, and how a few critical packages underpin enormous chunks of the internet.

The importlib module documentation. (Tier 2) Python's import system is itself implemented in Python (mostly). The importlib module exposes the internals of how import works. Advanced reading, but fascinating if you want to understand the machinery behind import.
Batchelder, N. "How Python Imports Work." Blog post. (Tier 2) Ned Batchelder's detailed walkthrough of the import system, including sys.path, finders, loaders, and the module cache. Excellent for understanding what happens "under the hood" when you write import something.