Python importing submodules from submodule

Question

I have got a problem when using python imports. I wrote a finished module, that itself uses several submodules (those are imported).

e.g.

module:
 main_class.py
 submodule1.py
 ....

Now I want to use this finished module by another supermodule, so the folder structure would change like this

supermodule:
 main_class_super.py -- this class imports module.main_class
 module:
 main_class.py
 submodule1.py
 ....

However now all imports that are used in the code of main_class.py inside the module fail (I guess because the import now works in the namespace of main_class_super.py)

Any idea how to solve this problem without restructuring the entire sources?

---

The concrete error:

In my main_class.py I use the line:

import submodule1

In my supermodule.py I use the line:

import module.main_class

When executing the superclass that imports module.main_class of course the import submodule1 line is executed as well, but fails as it can not find the module in the namespace of supermodule.py.

Answer 1

If you are on python 2 you should add from __future__ import absolute_import to your files (not needed on 3) so you can do the imports like Guido states in PEP 328

According to this you should

• Make sure all your package folders have a __init__.py in it to mark them as importable

• In main_class.py: replace import submodule1 or import module.submodule1 with from . import submodule1

• In main_class_super.py: replace import module.main_class with from .module import main_class

This way you don't have to care about any outer package structure.

The option to use absolute and explicit relative imports was added in Python 2.5.

• WodkaRHR: Er, i think i do not quite get how this can help me. Given my folder structure, how would i do the import of the submodule1.py inside the supermodule.py?
• WodkaRHR: Sorry to bother you again, by i encountered another problem. Inside those submodules several modules import the same other modules (e.g. submodule1 imports submodule2 and 3 and submodule2 also imports submodule3. Then this import inside submodule2 wont work. (even though i changed it to from . import submodule3). All other imports just work fine
• janbrohl: Sorry, without directory layout (what files are in what folders?) i cannot help on that
• WodkaRHR: Structure is the same, only that there is not only submodule1.py on the lowest level but also submodule2.py and submodule3.py.