Describe easmy/plugins here.
== Plugins ==
Bazaar comes with a wonderful plugins system.  The plugins when placed in  '''.bazaar/plugins/''' subdirectory, immediately become available to the user. What a fine way of enabling contribution from the community!

I am not a professional programmer, though I have programmed and taught programming for many years in many different programming languages. I was intrigued by the plugins system, though decided to do write a very simple program that would incorporate the capabilities of plugins.  It is very short and I will give a listing of it RSN. But first I better learn something about the rules of this wiki.

{{{#!python
#!/usr/bin/env python
#!/usr/bin/env python
''' fooboo.py - mainline of trial of dummy plugins
The aim is to try to imitate the plugin system of Bazaar, where a plugin placed in
...plugins/foo/ directory is recognised as "foo".
Plugin "foo" simply says "Hallo from Foo". Similarly, boo says "hallo from Boo".
'''
import os

def prolog():
    'Return list of subdirectories in plugins directory.'   
    temp = os.listdir(os.getcwd() + '/plugins')
    return [v for v in temp if not '.' in v] 
    
def import_plugins(listdirs):
    '''Import all available modules and their packages which are in 
    plugins/ directory'''
    module = {}
    for v in listdirs:
        pak = 'plugins.' + v + '.' + v + '_mod'
        print 'pak = ', pak
        # sample pak = plugins.foo.foo_mod
        try:
            plug = __import__(pak)
            # This imports foo.mod, foo and plugins. plugins are assigned to plug.
            module[v] = plug
        except:
            print 'Failed to import ', v
    return module

def main():
    'Do the main coordinating job.'
    listdirs = prolog()
    print listdirs
    module = import_plugins(listdirs)
    print module
    foo_inst = module['foo'].foo.foo_mod.Foo()
    foo_inst.sayhi()
    print 'Hey, Boo, speak to me too!'
    boo_inst = module['boo'].boo.boo_mod.Boo()
    boo_inst.sayhi()
    
if __name__ == '__main__':
    'Just call the main function.'
    main()
}}}

Suppose this "mainline" is in a directory foo_boo on your PC.  Directly under foo_boo is a plugins directory. In it is an empty __init__.py file.  That makes plugins a python package.  Directly under plugins are '''foo''' and '''boo''' directories. Each has an empty __init__.py to make them sub-packages.  In each there is a module - foo_mod.py and boo_mod.py:

This simple plugins system enables addition of plugins which will be recognised by the calling program as soon as they are placed in a plugins subdirectory.  Some fairly simple requirements: the module that can be called from the main program is expected to be of the name <plugin_directory>_mod.  The <plugin directory> must be a simple character string without any dots. Try to add a moo plugin with moo_mod module and perhaps the same class and procedure name as other plugins.  Also, try to get __init__.py to respond to invocation of the package.  It is activated at the time the package is loaded, If you wish, make it say something in a print statement,

{{{#!python
#!/usr/bin/env python
''' foo_mod.py - module.'''

class Foo:
    def __init__(self):
        return
    
    def sayhi(sel):
        print 'Hi from Mr Foo.'
}}}

and

{{{#!python
#!/usr/bin/env python
''' boo_mod.py - module.'''

class Boo:
    def __init__(self):
        return
    
    def sayhi(self):
        print 'I am Mr. Boo - boo to you too.'
}}}


Try it and watch the "conversation".  


return to  [[easmy]]