How can I flatten the namespace of just one module?

Question

I have the following simple project and package structure:

Project/
    package/
        __init__.py
        a.py
            class One: ...
            class Two: ...
        b.py
            from . import a
            class Three: ...
            class Four: ...

I want users to be able to use it as such:

import package
# or
from package import Three, Four
from package.a import One, Two
# or
from package import a

I've tried several uses of from...import in the __init__.py but to no avail! Here's a summary of what I've tried to put in Project/package/__init__.py and the errors they produced when attempting to import package:

from .b import Three, Four
#  ImportError: No module named 'package.b'  
---
from b import Three, Four
#  ImportError: No module named 'b'
---
from package.b import Three, Four
# ImportError: cannot import name Three

I thought I had already solved this problem in my last project... (see: this answer)

TL;DR What do I need to put in Project/package/__init__.py such that users can then import classes Three and Four directly from my package without needing to know in which module they exist? In other words, how can I flatten the namespace of module b?

Edit: using Python 3.3, but I may switch to 3.4 and I may also need to support 2.7.

Edit: added a TL;DR

Edit: significantly reformatted the question for clarity

Edit: updated title to reflect the clarity :)

Edit: added reference to a similar (solved) question that doesn't seem to work in this case

You might have circular imports. Do you have any imports in `a.py`? — Lukas Graf, Aug 09 '14 at 10:52
Possible duplicate of [Code style - "flattening" a package's namespace](https://stackoverflow.com/questions/12626336/code-style-flattening-a-packages-namespace) — Tom Myddeltyn, Dec 27 '18 at 02:51

Beta Decay · Answer 1 · 2014-08-09T11:10:56.293

0

You don't use the dot: it's as simple as that.

In b.py:

from a import Three, Four

It seems that your program is looking for a package.b, not just b. This probably means that using a . won't work

Output from from .a import

File "/storage/emulated/0/com.hipipal.qpyplus/scripts3/.last_tmp.py",   line 1, in <module>
from .a import One, Two
ValueError: Attempted relative import in non-package

Output from from a import (expected)

1
2

edited Aug 09 '14 at 11:10

answered Aug 09 '14 at 10:52

Beta Decay

805
1
8
20

And what if there is a package called `a`? – rhgrant10 Aug 09 '14 at 10:54
@rhgrant10 You'll have to rename your file – Beta Decay Aug 09 '14 at 10:54
@rhgrant Which version of Python are you using? – Beta Decay Aug 09 '14 at 10:55
Updated the question to indicate Python version :-) – rhgrant10 Aug 09 '14 at 10:59
@rhgrant From experimentation, by renaming a to time, I've found that Python favours the local scripts over the installed packages. – Beta Decay Aug 09 '14 at 11:23
Well I'm not getting a ValueError, I'm getting an ImportError. – rhgrant10 Aug 09 '14 at 11:50
I think you may not have an `__init__.py` file in that directory which is causing the `ValueError`. That is a very different error despite being caused by the same syntax. – rhgrant10 Aug 09 '14 at 11:55
@rhgrant10 Ahh yes. Is your __init__.py empty? – Beta Decay Aug 09 '14 at 11:57
1

That's the question: what do I need to put in it such that users can then import classes Three and Four directly from my package without needing to know in which module they exist. – rhgrant10 Aug 09 '14 at 12:00
I just tried `from b import Three, Four` and it produced another `ImportError`: ImportError: No module named 'b' – rhgrant10 Aug 09 '14 at 12:05

How can I flatten the namespace of just one module?

1 Answers1