SDN Module 6 Pyretic Firewall

pyretic_firewall.py

'''
    Coursera:
    - Software Defined Networking (SDN) course
    -- Module 6 Programming Assignment
    
    Professor: Nick Feamster
    Teaching Assistant: Muhammad Shahbaz
'''

################################################################################
# The Pyretic Project                                                          #
# frenetic-lang.org/pyretic                                                    #
# author: Joshua Reich (jreich@cs.princeton.edu)                               #
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from pyretic.lib.corelib import *
from pyretic.lib.std import *

from pyretic.modules.mac_learner import mac_learner as act_like_switch

import csv, os
policy_file = "%s/pyretic/pyretic/examples/firewall-policies.csv" % os.environ[ 'HOME' ]

def main():
    # start with a policy that doesn't match any packets
    not_allowed = none
    # and add traffic that isn't allowed
    with open(policy_file, 'rb') as f:
        reader = csv.DictReader(f)
        for row in reader:
            not_allowed = not_allowed + match(srcmac=MAC(row['mac_0']), dstmac=MAC(row['mac_1'])) + match(srcmac=MAC(row['mac_1']), dstmac=MAC(row['mac_0']))

    # express allowed traffic in terms of not_allowed - hint use '~'
    allowed = ~not_allowed
#    allowed = if_(not_allowed, drop, passthrough)

    # and only send allowed traffic to the mac learning (act_like_switch) logic
    return allowed >> act_like_switch()

Hi, change it into the following, in this way it will not be confused with parallel process:
with open(policy_file, 'rb') as f:
reader = csv.DictReader(f)

    for row in reader:
        temp =  match(srcmac=MAC(row['mac_0']), dstmac=MAC(row['mac_1'])) | \
                match(srcmac=MAC(row['mac_1']), dstmac=MAC(row['mac_0']))
        not_allowed = not_allowed | temp

from pyretic.lib.corelib import *
from pyretic.lib.std import *

from pyretic.modules.mac_learner import mac_learner as act_like_switch
import csv
from collections import namedtuple
import os

policy_file = "%s/pyretic/pyretic/examples/firewall-policies.csv" % os.environ[ 'HOME' ]

def main():

not_allowed = none

with open(policy_file, 'rb') as f:
    reader = csv.DictReader(f)

    for row in reader:
        temp =  match(srcmac=MAC(row['mac_0']), dstmac=MAC(row['mac_1'])) | \
                match(srcmac=MAC(row['mac_1']), dstmac=MAC(row['mac_0']))
        not_allowed = not_allowed | temp

allowed =~not_allowed


return allowed >> act_like_switch()

Does it work?
I got following error when I executed above code , the error is something like this

TypeError: list indices must be integers, not str