This demo shows how you can create and manage your own custom plugins for extending functionality in your Python projects. There are no safety wrappers in this demo for restricting plugins aside from that fact that plugins are run as an extention of a management class which is run in its own instance only receiving data passed to it by the RumModules method, that said security should ideally be applied to the ModuleAPI class, by restricting __builtins__ on eval calls and/or validating plugin content and parameters which can be done by extending the Prepaser Class. For a great recipe/demo of restricting eval call see http://code.activestate.com/recipes/496746.
That aside it was alot of fun to write and use. Enjoy
PS: you will need http://code.activestate.com/recipes/577144/ to import Xceptions
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from array import array
from Xceptions import XceptionHandler
"""
PluginManager
Author: AJ Mayorga
Date: 5/5/2010
** Here Module and Plugin are used interchangably to refer to custom
code provided during runtime of a project to provide additional
functionality. Not the import of a proper Python module **
A Demo And Framework For Creating Plugins/Modules For Python Projects.
Providing For:
- Modules contain there own pragma section for config vars
- Pragma sections are read and validated by Preparser before evaluating/executing
- Checks for necessary config vars
- Checks module dependencies
- Modules can be run inline or inside of their own thread
- Provides for module garbage collection
"""
#Some Constants For Use with Xceptions
EXC_RETURN = -1 # Report Exception and return ie continue on
EXC_RAW = -2 # Report on and return a traceback dump as dict() then continue
EXC_RAISE = -3 # Report on & raise the exception do not continue
########################################################
# Thanks to Daniel Brodie for the how to on Extending Classes
# http://code.activestate.com/recipes/412717
def get_obj(name): return eval(name)
class ExtendInplace(type):
def __new__(self, name, bases, dict):
prevclass = get_obj(name)
del dict['__module__']
del dict['__metaclass__']
for k,v in dict.iteritems():
setattr(prevclass, k, v)
return prevclass
########################################################
"""
Exception Class For Our Preparser
we'll use this when we want to raise on a
logic failure
"""
class ModuleParserException(Exception):
def __init__(self, value):
self.parameter = value
def __str__(self):
return repr(self.parameter)
"""
Reading in the Pragma Section from the Module get config parameters
Ensure Module has needed parameters and check module dependencies
"""
class Preparser(XceptionHandler):
def __init__(self):
self.name = str(self.__class__).split(".")[1]
XceptionHandler.__init__(self, DEBUG=False)
#Modules Are Required To Have These Config Parameters
self.params = ['_NAME_','_AUTHOR_','_DATE_','_DEPENDS_','_ON_EXC_','_RUN_']
def Parser_Xception(self, *args):
return self.ProcessReturn(self.name, args)
def DependencyCheck(self, Modules):
try:
depends = list()
ModuleNames = [Module['_NAME_'] for Module in Modules]
for Module in Modules:
count = 0
for d in Module['_DEPENDS_']:
if not d in ModuleNames:
msg = "MODULE: "+Module['_NAME_']+" Failed Dependency Check"
msg += " Dependency "+d+" Could Not Be Found"
raise ModuleParserException(msg)
except:
self.Parser_Xception(EXC_RAISE)
def LoadModules(self, Modules):
ModulesOut = list()
try:
for Module in Modules:
Module = self.ProcessModule(Module)
ModulesOut.append(Module)
self.DependencyCheck(ModulesOut)
for Module in ModulesOut:
yield Module
except:
self.Parser_Xception(EXC_RAISE)
def ProcessModule(self, Module):
try:
ModuleOut = dict()
StartTag = "PRAGMA_START"
EndTag = "PRAGMA_END"
pragma_section = Module[Module.find(StartTag)+len(StartTag):Module.rfind(EndTag)-1].strip()
args = pragma_section.split('\n')
for x in args:
key, value = x.split('=')
key = key.replace(" ", "")
key = key.replace("self.", "")
value = value.replace(" ", "")
ModuleOut[key] = eval(value)
ModuleOut['CODE'] = Module
moduleName = ModuleOut.get('_NAME_', "Unknown")
for param in self.params:
if not ModuleOut.has_key(param):
raise ModuleParserException("MODULE: "+moduleName+" PRAGMA SECTION IS MISSING: "+param)
return ModuleOut
except:
self.Parser_Xception(EXC_RAISE)
"""
Plugin/Module Manager Class, All modules will run as an extention of this class
"""
class ModuleAPI(XceptionHandler, Preparser):
def __init__(self):
self.name = str(self.__class__).split(".")[1]
XceptionHandler.__init__(self, DEBUG=False)
Preparser.__init__(self)
"""
These vars the the only intended vars meant to survive module runs
other objects created by the module will be cleaned up after run
"""
self.ModuleARGS = None
self.ModuleName = ""
self.ModuleDataStor = None
self.ModuleReturn = None
self.ModuleXceptionHandler = XceptionHandler(DEBUG=True)
self.ModuleOnException = ""
self.OrigObjects = None
def ModuleAPI_Xception(self, *args):
return self.ProcessReturn(self.name, args)
def ModuleXception(self, *args):
return self.ModuleXceptionHandler.ProcessReturn(self.ModuleName, args)
"""
Really this is a place holder, just printing, but can be called from within the module
to relay messages to DB,Server,Parent Process etc.
"""
def Callback(self, Message):
print Message
"""
Here we check to see what objects have been created during our module run
and delete them garbage collection of sorts.
This helps with object naming issues between modules, conserving resources etc.
"""
def CleanUp(self):
cleanup = list()
for k, v in self.__dict__.iteritems():
if not self.OrigObjects.has_key(k):
cleanup.append(k)
for old in cleanup:
del self.__dict__[old]
"""
Where we bring it all together
"""
def RunModules(self, Modules, Args):
ret = True
self.OrigObjects = self.__dict__.copy()
for Module in self.LoadModules(Modules):
try:
self.ModuleName = Module['_NAME_']
self.ModuleOnException = Module['_ON_EXC_']
self.ModuleARGS = Args
print "STARTING NEW MODULE RUN: ",self.ModuleName,"\n"
eval(compile(Module['CODE'], sys.argv[0], "exec"))
if Module['_RUN_'] == 'INLINE':
self.Run()
elif Module['_RUN_'] == 'THREAD':
self.lock=thread.allocate_lock()
self.lock.acquire()
thread.start_new_thread ( self.Run, () )
self.lock.acquire()
self.Callback(self.ModuleName+" Output:"+self.ModuleDataStor.tostring()+"\n")
except:
self.Callback(self.ModuleAPI_Xception(self.ModuleOnException))
ret = False
break
finally:
self.ModuleARGS = None
self.CleanUp()
print "ENDING MODULE RUN: ",self.ModuleName,"\n\n"
return ret
Module1 = """
class ModuleAPI:
__metaclass__ = ExtendInplace
def Init(self):
try:
__name__ = self.ModuleName
#PRAGMA_START
self._NAME_ = 'VModule_Test1'
self._AUTHOR_ = 'AJ Mayorga'
self._DATE_ = 'May 1, 2010'
self._DESCRIPTION_ = 'Test Plugin'
self._DEPENDS_ = ()
self._ON_EXC_ = EXC_RETURN
self._RUN_ = 'INLINE'
#PRAGMA_END
if self.ModuleDataStor:
self.DataBuffer = self.ModuleDataStor
else:
self.DataBuffer = self.ModuleARGS['DataBuffer']
self.Return = False
except:
self.ModuleXception(self._ON_EXC_)
def Run(self):
try:
self.Init()
self.Callback(self.ModuleName+" Input: "+self.DataBuffer.tostring())
self.ModData()
self.ModuleDataStor = self.DataBuffer
self.Return = True
except:
self.ModuleDataStor = self.ModuleARGS['DataBuffer']
self.ModuleXception(self._ON_EXC_)
finally:
self.ModuleReturn = self.Return
if self._RUN_ == 'THREAD':
print self.ModuleName,"Exiting From Thread: ",thread.get_ident()
lock.release()
def ModData(self):
try:
import string
temp = self.DataBuffer.tostring()
temp = string.replace(temp, "SCARY", "HAPPY")
self.DataBuffer = array('B', temp)
except:
return self.ModuleXception(self._ON_EXC_)
"""
Module2 = """
class ModuleAPI:
__metaclass__ = ExtendInplace
def Init(self):
try:
__name__ = self.ModuleName
#PRAGMA_START
self._NAME_ = 'VModule_Test2'
self._AUTHOR_ = 'AJ Mayorga'
self._DATE_ = 'May 1, 2010'
self._DESCRIPTION_ = 'Test Plugin'
self._DEPENDS_ = ('VModule_Test1', 'VModule_Test3')
self._ON_EXC_ = EXC_RETURN
self._RUN_ = 'THREAD'
#PRAGMA_END
if self.ModuleDataStor:
self.DataBuffer = self.ModuleDataStor
else:
self.DataBuffer = self.ModuleARGS['DataBuffer']
self.Return = False
except:
self.ModuleXception(self._ON_EXC_)
def Run(self):
try:
self.Init()
self.Callback(self.ModuleName+" Input: "+self.DataBuffer.tostring())
self.ModData()
self.ModuleDataStor = self.DataBuffer
self.Return = True
except:
self.ModuleDataStor = self.ModuleARGS['DataBuffer']
self.ModuleXception(self._ON_EXC_)
finally:
self.ModuleReturn = self.Return
if self._RUN_ == 'THREAD':
print self.ModuleName,"Exiting From Thread: ",thread.get_ident()
self.lock.release()
def ModData(self):
try:
import string
temp = self.DataBuffer.tostring()
temp = string.replace(temp, "RECTAL", "LITTLE")
self.DataBuffer = array('B', temp)
except:
return self.ModuleXception(self._ON_EXC_)
"""
Module3 = """
class ModuleAPI:
__metaclass__ = ExtendInplace
def Init(self):
try:
__name__ = self.ModuleName
#PRAGMA_START
self._NAME_ = 'VModule_Test3'
self._AUTHOR_ = 'AJ Mayorga'
self._DATE_ = 'May 1, 2010'
self._DESCRIPTION_ = 'Test Plugin'
self._DEPENDS_ = ('VModule_Test1', 'VModule_Test2')
self._ON_EXC_ = EXC_RETURN
self._RUN_ = 'INLINE'
#PRAGMA_END
if self.ModuleDataStor:
self.DataBuffer = self.ModuleDataStor
else:
self.DataBuffer = self.ModuleARGS['DataBuffer']
self.Return = False
except:
self.ModuleXception(EXC_RETURN)
def Run(self):
try:
self.Init()
self.Callback(self.ModuleName+" Input: "+self.DataBuffer.tostring())
self.ModData()
self.ModuleDataStor = self.DataBuffer
self.Return = True
except:
self.ModuleDataStor = self.ModuleARGS['DataBuffer']
self.ModuleXception(self._ON_EXC_)
finally:
self.ModuleReturn = self.Return
if self._RUN_ == 'THREAD':
print self.ModuleName," Exiting From Thread: ",thread.get_ident()
lock.release()
def ModData(self):
try:
import string
temp = self.DataBuffer.tostring()
temp = string.replace(temp, "THERMOMETERS", "TREES")
self.DataBuffer = array('B', temp)
except:
return self.ModuleXception(EXC_RAISE)
"""
if __name__ == '__main__':
Modules = [Module1, Module2, Module3]
ARGS = dict()
ARGS['DataBuffer'] = array('B', "SCARY RECTAL THERMOMETERS")
ModAPI = ModuleAPI()
#Call One
print "Running One Module"
ModAPI.RunModules([Module1], ARGS)
print "Single Module Output: ", ModAPI.ModuleDataStor.tostring()
print "\n\n"
#Call Them All
print "Running All Modules"
ModAPI.RunModules(Modules, ARGS)
print "Module Group Output: ",ModAPI.ModuleDataStor.tostring()
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