Plugin system; imp module head scratch

[Dave]

Hi, all,

I'm trying to implement a simple plugin framework, with some
unexpected results. I'm using Python 2.3.4 on Windows 2000.

My script loader.py loads plugin packages from a directory (in this
case its own), and checks a variable defined in the package's
__init__.py for information on the plugin.

The directory in which loader.py sits is itself a package::

plugin_test
|
+ Plugin1
| |
| __init__.py
|
__init__.py
loader.py

I must be misunderstandin g how the imp module works, or something.
Although the correct package is returned by my helper method, its
member variables are those of the the parent package, plugin_test.

The output of this demo is::

<module 'Plugin1' from '__init__.pyc'>
Directory plugin_test

Which seems contradictory. What have I got wrong?

Best Regards,

Dave

<Code follows>

This is plugin_test/Plugin1/__init__.py::

dir = "plugin_tes t/Plugin1"


This is plugin_test/__init__.py::

dir = "plugin_tes t"


And here is the loader script, plugin_test/loader.py::

import os
import imp

def GetPackage(name , peerFile, relPath = '.'):
"""
Return the named Python package on a
relative path from the file given
"""
path = os.path.normpat h(
os.path.join(os .path.dirname(p eerFile), relPath))
try:
fObj, path, descr = imp.find_module (name, [path])
except ImportError:
return None
if descr[2] != imp.PKG_DIRECTO RY:
return None
try:
return imp.load_module (name, None, '', descr)
except:
return None

if __name__ == "__main__":
pkg = GetPackage("Plu gin1", __file__, '.')
print pkg
print "Directory ", pkg.dir

[Keith Dart]

Re: Plugin system; imp module head scratch

Dave wrote:[color=blue]
> Hi, all,
>
> I'm trying to implement a simple plugin framework, with some
> unexpected results. I'm using Python 2.3.4 on Windows 2000.[/color]

What would be the difference between a "plugin" and a regular Python module?



-- ~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~ ~~~~~~~~~
Keith Dart <kdart@kdart.co m>
public key: ID: F3D288E4
=============== =============== =============== =============== =========

[Nick Coghlan]

Re: Plugin system; imp module head scratch

Dave wrote:[color=blue]
> Hi, all,
>
> I'm trying to implement a simple plugin framework, with some
> unexpected results. I'm using Python 2.3.4 on Windows 2000.
>
> My script loader.py loads plugin packages from a directory (in this
> case its own), and checks a variable defined in the package's
> __init__.py for information on the plugin.[/color]

Packages and modules are really rather different beasts. I wouldn't be surprised
to find that 'find_module' and 'load_module' behave strangely when used for
packages.

Is there any reason you can't temporarily alter sys.path and use __import__
normally? The behaviour of that is generally less quirky.


Anyway, I believe your specific problem is this line:
return imp.load_module (name, None, '', descr)

Try replacing the empty string in the third argument with the path returned from
the find_module call. (At the moment, it is pulling in the __init__.py from the
current directory, and assigning it to the name you requested)

Cheers,
Nick.

--
Nick Coghlan | ncoghlan@email. com | Brisbane, Australia
---------------------------------------------------------------

http://boredomandlaziness.skystorm.net