user modules

[Cameron Walsh]

Juho Schultz wrote:
> Juho Schultz wrote:
>> Cameron Walsh wrote:
>>> Hi,
>>>
>>> I'm writing a python program to analyse and export volumetric data.  To
>>> make development and extension easier, and to make it more useful to the
>>> public when it is released (LGPL), I would like to enable users to place
>>> their own python files in a "user_extensions" directory.  These files
>>> would implement a common interface in order for the main program to be
>>> able to read them and execute the necessary code.
>>>
>>> My question is what is the best way of implementing this?
>>>
>>> I have investigated importing them as modules, but unless the user
>>> modifies the main program I cannot see how the main program can learn of
>>> the existence of specific modules.
>>>
>> One simple solution would be a shell script that adds user_extensions
>> (or whatever) to $PYTHONPATH and then starts your main program.
> 
> Sorry... I was typing faster than reading or thinking.
> 
> You could have a __init__.py file within user_extensions with
> __all__ = ["package1", "package2"]
> 
> If you want every python file within some directory in here, you can
> auto-generate the __init__.py file in user_extension before importing.
> (Or you could have some sort of tester for new .py files detected and
> only after you are sure it works, add it.)
> 
> from user_extensions import *
> 
> would import everything mentioned in __all__. You also have access to
> their names through
> user_extensions.__all__
> 
> The last step would be to put the modules into a list. After the
> import,
> 
> user_ext_list = [eval(elem) for elem in user_extensions.__all__ ]
> for ext in user_ext_list:
>     ext.initialize()
>     ext.get_tab_window()
> 

Thanks Juho,

Your solution also worked a charm.  I like the suggestion of a tester 
before adding a module to the __all__ list.

Thanks for teaching me about the eval() function, I've been wondering 
how to turn a string into a python command.