python-patterns/chain.py at master · masterp4dev/python-patterns · GitHub

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""http://www.testingperspective.com/wiki/doku.php/collaboration/chetan/designpatternsinpython/chain-of-responsibilitypattern"""

classHandler:
def__init__(self,successor):
self._successor=successor;
defhandle(self,request):
i=self._handle(request)
ifnoti:
self._successor.handle(request)
def_handle(self, request):
raiseNotImplementedError('Must provide implementation in subclass.')


classConcreteHandler1(Handler):

def_handle(self, request):
if0<request<=10:
print('request {} handled in handler 1'.format(request))
returnTrue

classConcreteHandler2(Handler):

def_handle(self, request):
if10<request<=20:
print('request {} handled in handler 2'.format(request))
returnTrue

classConcreteHandler3(Handler):

def_handle(self, request):
if20<request<=30:
print('request {} handled in handler 3'.format(request))
returnTrue
classDefaultHandler(Handler):

def_handle(self, request):
print('end of chain, no handler for {}'.format(request))
returnTrue


classClient:
def__init__(self):
self.handler=ConcreteHandler1(ConcreteHandler3(ConcreteHandler2(DefaultHandler(None))))
defdelegate(self, requests):
forrequestinrequests:
self.handler.handle(request)


if__name__=="__main__":
client=Client()
requests= [2, 5, 14, 22, 18, 3, 35, 27, 20]
client.delegate(requests)

### OUTPUT ###
# request 2 handled in handler 1
# request 5 handled in handler 1
# request 14 handled in handler 2
# request 22 handled in handler 3
# request 18 handled in handler 2
# request 3 handled in handler 1
# end of chain, no handler for 35
# request 27 handled in handler 3
# request 20 handled in handler 2