class Handler (object):
"""The base class for all the handlers"""
def __init__(self):
self.data = {}
self.nextHandler = None
def __add__(self, newHandler):
"""Used to append handlers to each other"""
if not isinstance(newHandler, Handler):
raise TypeError('Handler.__add__() expects Handler')
if self.nextHandler:
self.nextHandler + newHandler
else:
self.nextHandler = newHandler
while newHandler:
newHandler.data = self.data
newHandler = newHandler.nextHandler
return self
def useHook(self, fileName):
"""Wrapper around the hook method"""
if self.nextHandler:
if not self.nextHandler.useHook(fileName):
return False
else:
self.data.clear( )
return self.hook(fileName)
def hook(self, fileName):
"""Default hook method to be overridden in subclasses"""
return True
# Subclasses of Handler
import os, time
class Filter (Handler):
def hook(self, fileName):
if fileName[-3:] == '.py':
return True
else:
return False
class Processor (Handler):
def hook(self, fileName):
modtime = os.path.getmtime(fileName)
if (time.time()- modtime) < 24*60*60:
self.data['state']='changed'
self.data['modtime']=time.ctime(modtime)
else:
self.data['state']='unchanged'
return True
class Logger (Handler):
def hook(self, fileName):
print fileName,
for key in self.data.keys():
print '%s=%s' % (key, self.data[key]),
print
return True
# Script that shows the use of a handler stack
if '__main__'==__name__:
import sys
a=Logger( )
b=Processor( )
c=Filter( )
d=a+b+c
for dirPath, dirNames, fileNames in os.walk(sys.argv[1]):
for fileName in fileNames:
d.useHook(os.path.join(dirPath, fileName))
