Supply a plugin interface

[Steven D'Aprano]

On Thu, 23 Apr 2009 09:47:56 +0200, Johannes Bauer wrote:

> Hello group,
> 
> I'm developing a GUI application in Python and having a blast so far :-)
> 
> What I'd like to add: I want the GUI users to supply plugin scripts,
> i.e. offer some kind of API. That is, I want the user to write short
> Python pieces which look something like
> 
> import guiapp
> 
> class myplugin():
> 	def __init__(self):
> 		guiapp.add_menu("foobar")
> 
> 	def exec(self, param):
> 		print("foo")

"exec" is a reserved word:

>>> def exec(self, param):
  File "<stdin>", line 1
    def exec(self, param):
           ^
SyntaxError: invalid syntax


> the GUI application should now browse the plugin directory and read
> those plugin python files and somehow incorporate (i.e. discover what
> modules are there, instanciate, etc.)
> 
> How do I do that at runtime with Python?

Untested:

import os
import sys
plugin_dir = os.path.expanduser('~/some/path/')
plugins = set()
for name in os.listdir(plugin_dir):
    base, ext = os.path.splitext(name)
    if ext in ('.py', '.pyc', '.pyo'):
        plugins.add(base)
save_path = sys.path
plugin_modules = []
try:
    sys.path = [plugin_dir]
    for name in plugins:
        plugin_modules.append(__import__(name))
finally:
    sys.path = save_path




Hope this is useful.


-- 
Steven