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How is it possible build multiple python modules sharing the same namespace compatible for Python 2.7+ and 3.3+?

Let's call the namespace test. Now I want to have two seperate modules called test.foo and another one called test.bar. However, I'm currently developing test.helloworld which depends on both, test.foo and test.bar. Both are listed in the requirements.txt file.

The modules test.foo and test.bar are currently using the Python 2 solution for namespace packages:

import pkg_resources
pkg_resources.declare_namespace(__name__)

Running the suggested pip-command for development mode pip install -e . turns into: ImportError: No module named 'test.helloworld' while importing test.foo or test.bar is working.

The Python 3 solution for namespace packages are Implicit Namespace Packages where the namespace package has no __init__.py file. This is sadly not working for Python 2 versions.

How can I design a solution for both Python 2 and 3 (which allows me to use pip install -e .)? The --egg solution does not work for me since it is already deprecated.

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floqqi
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3 Answers3

1

I recently had a similar issue, where I had to install a package for Python 2 and 3. I ended up having to download the code from GitHub, then ran the setup.py by calling

sudo python setup.py install

and

sudo python3 setup.py install

This results in the package being installed for both Python 2 and 3, even though the code itself was meant for Python 2. This allows me to work with the package whether I use Python 2 or 3, without any namespace conflicts.

awkbr549
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1

You'd want to use pkgutil-style namespace packages.

From https://packaging.python.org/guides/packaging-namespace-packages/:

pkgutil-style namespace packages

Python 2.3 introduced the pkgutil module and the extend_path function. This can be used to declare namespace packages that need to be compatible with both Python 2.3+ and Python 3. This is the recommended approach for the highest level of compatibility.

A table listing out all the possible ways of dealing with namespace packages, and which ways would work together: https://github.com/pypa/sample-namespace-packages/blob/master/table.md

pradyunsg
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0

See the answer at similar question for complete instructions which works on both python 2 and 3.

In short, setup.py needs to have unique name for each module and a common namespace_packages definition in addition to __init__.py declaring the namespace set at namespace_packages.

If you are still having issues, please post your setup.py and __init__.py for each module.

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danny
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