Learning Python, 5th Edition

Chapter 22. Modules: The Big Picture

This chapter begins our in-depth look at the Python module—the highest-level program organization unit, which packages program code and data for reuse, and provides self-contained namespaces that minimize variable name clashes across your programs. In concrete terms, modules typically correspond to Python program files. Each file is a module, and modules import other modules to use the names they define. Modules might also correspond to extensions coded in external languages such as C, Java, or C#, and even to directories in package imports. Modules are processed with two statements and one important function:

import

Lets a client (importer) fetch a module as a whole

from

Allows clients to fetch particular names from a module

imp.reload (reload in 2.X)

Provides a way to reload a module’s code without stopping Python

Chapter 3 introduced module fundamentals, and we’ve been using them ever since. The goal here is to expand on the core module concepts you’re already familiar with, and move on to explore more advanced module usage. This first chapter reviews module basics, and offers a general look at the role of modules in overall program structure. In the chapters that follow, we’ll dig into the coding details behind the theory.

Along the way, we’ll flesh out module details omitted so far—you’ll learn about reloads, the __name__ and __all__ attributes, package imports, relative import syntax, 3.3 namespace packages, and so on. Because ...