Learning Python, 5th Edition

Chapter 24. Module Packages

So far, when we’ve imported modules, we’ve been loading files. This represents typical module usage, and it’s probably the technique you’ll use for most imports you’ll code early on in your Python career. However, the module import story is a bit richer than I have thus far implied.

In addition to a module name, an import can name a directory path. A directory of Python code is said to be a package, so such imports are known as package imports. In effect, a package import turns a directory on your computer into another Python namespace, with attributes corresponding to the subdirectories and module files that the directory contains.

This is a somewhat advanced feature, but the hierarchy it provides turns out to be handy for organizing the files in a large system and tends to simplify module search path settings. As we’ll see, package imports are also sometimes required to resolve import ambiguities when multiple program files of the same name are installed on a single machine.

Because it is relevant to code in packages only, we’ll also introduce Python’s recent relative imports model and syntax here. As we’ll see, this model modifies search paths in 3.X, and extends the from statement for imports within packages in both 2.X and 3.X. This model can make such intrapackage imports more explicit and succinct, but comes with some tradeoffs that can impact your programs.

Finally, for readers using Python 3.3 and later, its new namespace package ...