Developing with Python Namespaced Packages

Question

I am having an issue with python namespaced packages and am wondering what is a good solution.

My project structure is similar to the following

project_name/ext/app_ext

That is the project I'm working on. It has dependencies that are also in the same namespace.

project_name/ext/base_ext
project_name/ext/other_dependency

I am working on the "app_ext" namespaced package in a django application. However, I am running into issues receiving a no module named app_ext.

I think it has to do with how the dependency namespaced packages are installed (I'm installing with PIP). The dependency namespaced packages aren't installed with the __init__.py files as is documented in the distribute / setuptools documentation, but all truly contain the following declarations in their installation packages.

from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)

Now to the real question. Is there a trick to working with a namespaced package when there is already some related namespaced packages installed?

Answer 1

One solution is to modify the path of the namespaced package to add your local path. (if you are working in Django, you could add a snippet like the following to your settings.py).

from os import path
import sys

PACKAGE_NAMESPACE = ["project_name", "ext"]
VIRTUAL_PACKAGE = '.'.join(PACKAGE_NAMESPACE)
__import__(VIRTUAL_PACKAGE)
local_package = path.abspath(path.join(*PACKAGE_NAMESPACE))
sys.modules[VIRTUAL_PACKAGE].__dict__["__path__"].insert(0, local_package)

This approach is also used in the tiddlyweb project for the tiddlywebplugins namespace.