py-impala

Import packages and modules from arbitrary directories and files

Author: Roman Neuhauser
Contact: neuhauser@sigpipe.cz
Copyright: This document is in the public domain.

Overview

Impala is a PEP302 protocol (sys.meta_path hook for the import statement) implementation allowing the user to import packages and modules from arbitrarily named directories and files.

Motivation

Comfort and freedom in development
Installed interface available without installation

Let's say I'm developing a Python package called pyoneer. I want to lay the source code out like this: :

README.txt
src/
  __init__.py
  some.py
  more.py
tests/
  ...

The question then is, how do I import pyoneer in the test files (<workdir>/tests/...) and have it load <workdir>/src/__init__.py? The default import mechanism requires packages to live in eponymous directories.

What's the fuss about, you ask? I should simply rename the src directory to pyoneer or maybe src/pyoneer, no?

Indeed, this would be tolerable, at least with top-level packages. However, if I'm working on something that will be available as foo.bar.baz after installation, I certainly don't want to wade through the desolate src/foo/bar to get to the source code.

Maybe I could import src in the tests instead? Well, tests are a form of documentation, and doubly so with doctest. "Proper" documentation (README.txt, etc) can also contain snippets which should be verifiable without the CUT being installed.

Impala to the rescue!

from os.path import abspath, dirname
import impala

root = abspath(dirname(__file__))

impala.register(dict(
  pyoneer = '%s/src' % root
))

import pyoneer

Description

`impala.register(aliases)`

aliases is a dict mapping from fully-qualified module/package names to paths to load from. To import a package p from path /a/b/c, aliases must include the key p with associated value /a/b/c, and /a/b/c/__init__.py must be a valid package entry point. To import a module m from path /f/g/h.py, aliases must include the key m with associated value /f/g/h.py.

Example: :

from os.path import abspath, dirname
import impala

r = dirname(abspath(__file__))

impala.register({
  'p': '%s/a/b/c' % r,
  'p.q': '%s/f/g/h' % r,
  'p.q.m': '%s/k.py' % r,
})

import p
import p.q
import p.q.m

License

py-impala is distributed under the MIT license. See LICENSE for details.

Installation

Using pip from PyPI, the Python Package Index: :

pip install impala

From a checkout or extracted tarball: :

python setup.py install

Development

Source code and issue tracker are at Github:

https://github.com/roman-neuhauser/py-impala