dictはsetで引き算できないので、一回、tupleにしてからsetで演算してdictに戻すテスト

addr.py

# dictはsetで引き算できないので、一回、tupleにしてからsetで演算してdictに戻すテスト
before = [{'netmask': '32', 'ipAddr': '192.168.0.1'}, {'netmask': '32', 'ipAddr': '213.199.128.119'}]
after = [{'netmask': '32', 'ipAddr': '192.168.0.1'}, ]

print("before: {0}".format(before))
print("after: {0}".format(after))
#before: [{'netmask': '32', 'ipAddr': '192.168.0.1'}, {'netmask': '32', 'ipAddr': '213.199.128.119'}]
#after: [{'netmask': '32', 'ipAddr': '192.168.0.1'}]

addrList2addrTuple = lambda x: (x["netmask"], x["ipAddr"])
beforeTuple = list(map(addrList2addrTuple, before))
afterTuple = list(map(addrList2addrTuple, after))

print("beforeTuple: {0}".format(beforeTuple))
print("afterTuple: {0}".format(afterTuple))
# beforeTuple: [('32', '192.168.0.1'), ('32', '213.199.128.119')]
# afterTuple: [('32', '192.168.0.1')]

result = set(beforeTuple) - set(afterTuple)
print("beforeTuple - afterTuple(set): {0}".format(result))
#beforeTuple - afterTuple(set): {('32', '213.199.128.119')}

addrTuple2addrList = lambda x: {"netmask": x[0], "ipAddr": x[1]}
resultDict = list(map(addrTuple2addrList, result))
print("beforeTuple - afterTuple(dict): {0}".format(resultDict))
# beforeTuple - afterTuple(dict): [{'netmask': '32', 'ipAddr': '213.199.128.119'}]