Python Plugins

Today I will tell how to build a plugin architecture in python on include'ah.




Our application will receive commands and distribute them to plugins in the hope that some plugin will even process it.
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Tricky plan

• When starting, scan the folder with plugins
• Import all found files
• When receiving a command, we send it to each plugin.

main.py

This contains only the code of the “external” part of the example, and I hope it is not necessary to comment on it.

Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])

1. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
3. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
5. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
7. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
8. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
9. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
10. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
12. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])
13. Copy Source | Copy HTML import plugin plugin.LoadPlugins() s = '' while (s != 'exit' ): print '>' , s = raw_input () a = s.split( ' ' ) for p in plugin.Plugins: p.OnCommand(a[ 0 ], a[ 1 :])

All plugin related code is in plugin.py.

plugin.py

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1. import os
2. import sys
4. # Instances of downloaded plugins
5. Plugins = []
7. # Basic class of the plugin
8. class Plugin (object):
9. Name = 'undefined'
11. # Feedback methods
12. def OnLoad (self):
13. pass
15. def OnCommand (self, cmd, args):
16. pass
19. def LoadPlugins ():
20. ss = os .listdir ( 'plugins' ) # Get the list of plugins in / plugins
21. sys .path.insert ( 0 , 'plugins' ) # Add the plugins folder to $ PATH so that __import__ can load them
23. for s in ss:
24. print 'Found plugin' , s
25. __import__ ( os .path.splitext (s) [ 0 ], None, None, [ '' ]) # Import the source of the plugin
27. for plugin in Plugin .__ subclasses __ (): # since the Plugin is derived from object, we use __subclasses__ to find all the plugins produced from this class
28. p = plugin () # Create an instance
29. Plugins.append (p)
30. p. OnLoad () # Call the event of loading this plugin
32. return

plugins / foo.py - plugin example

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1. from plugin import plugin
3. class HelloPlugin (Plugin): # produce our plugin from the parent class
4. Name = 'HelloPlugin v 1.0 Extreme Edition'
6. # replace the necessary methods
7. def OnLoad (self):
8. print 'HelloPlugin 1.0 Extreme VIP Edition Loaded!'
10. def OnCommand (self, cmd, args):
11. if (cmd == 'hello' and len (args)> 0 ):
12. print 'It \' s' , args [ 0 ], '! \ nJeez, man, nice to meet you!'
13. return true
14. else :
15. return false

Now you can run an example:

$ python main.py
Found plugin foo.py
HelloPlugin 1.0 Extreme VIP Edition Loaded!
> hello% username%
It's% username%!
Jeez, man, nice to meet you!
>

plugins / shell.py - the plugin is more complicated

Let's make a plugin that will broadcast commands to the shell and return the output:

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1. from plugin import plugin
2. import commands
4. class ShellPlugin (Plugin):
5. Name = 'Shell plugin'
7. def OnLoad (self):
8. print 'Shell plugin loaded.'
10. def OnCommand (self, cmd, args):
11. if (cmd == 'run' ):
12. print commands .getoutput ( "" .join (args))
13. return true
14. else :
15. return false

$ python main.py
Found plugin shell.py
Found plugin foo.py
Shell plugin loaded.
HelloPlugin 1.0 Extreme VIP Edition Loaded!
> run uname -r
2.6.31-14-generic
> exit

That's all!
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