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Editorial Team
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Asked: 2026-06-04T16:17:11+00:00

Why do I have to import all sub-packages if I want to use them?

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Why do I have to import all sub-packages if I want to use them?
I’ll explain myself with an example:

In [1]: import cime

In [2]: cime.runners
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/home/miki/testit/<ipython-input-2-35e09c66121a> in <module>()
----> 1 cime.runners

AttributeError: 'module' object has no attribute 'runners'

In [3]: import cime.runners

In [4]: cime.runners
Out[4]: <module 'cime.runners' from '/home/miki/testit/venv/lib/python2.7/site-packages/cime/runners/__init__.pyc'>

As you can see it’s a regular Python package:

In [5]: cime.__file__
Out[5]: '/home/miki/testit/venv/lib/python2.7/site-packages/cime/__init__.pyc'

In [6]: ls /home/miki/testit/venv/lib/python2.7/site-packages/cime
download.py   __init__.py   log.py   runners/  run.pyc   utils.pyc
download.pyc  __init__.pyc  log.pyc  run.py    utils.py

But this does not happens with built-in modules. Why?

In [7]: import os  # instead of import os.path

In [8]: os.path
Out[8]: <module 'posixpath' from '/home/miki/testit/venv/lib/python2.7/posixpath.pyc'>

Thanks,
rubik

P.S. I’m inside a virtualenv, but I don’t know if that matters.

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1 Answer

  1. Editorial Team

    This is a design decision by the cime (whatever that is) developers. A package does not magically import all of its subpackages. That’s a good thing, because otherwise large packages like SciPy would take forever to import (like NLTK does).

    Some packages, like os.path, NumPy and NLTK will import submodules, but they do so explicitly. If you want this to happen in your own module, do

    # __init__.py
import .submodule
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