[Zope-dev] Coding style clarifications

[Martijn Faassen]

Hi there,

Jim Fulton wrote:
[snip]
>> I suspect there are two possibilities:
>>
>> * no API defined in __init__.py and absolute imports
>>
>> * API defined in __init__.py and dotted.package.name.references  
>> don't work.
> 
> In what way don't they work?

> I don't see how this has anything to do with from imports.  Putting an  
> API in the package __init__ just makes object paths shorter.  I don't  
> see how the location of an API has much bearing on whether to use from  
> imports or not.

You generate circular imports if a package that does this has modules 
that contain absolute dotted imports from the same package, as I 
described elsewhere. If you use from imports in the modules in the 
package it does work. For imports of stuff that is external to the 
package it usually shouldn't matter (unless I guess there's a circular 
dependency between packages).

What causes this exactly caused us quite a bit of headscratching back at 
the sprint, and a lot of theorizing, but if anything satisfactory came 
out of that it's slipped my mind again. The interactions are quite 
subtle and changing an import from one form to the other (and having 
imports in __init__.py at all) can break it.

We discovered this when Christian Theune said he wanted his package 
__init__.py empty as otherwise he runs into circular import issues. Some 
of the others including myself were puzzled as we put APIs in 
__init__.py quite frequently without such problems. Turned out it was 
because he is using the same convention for imports you do, and we weren't.

Regards,

Martijn