Ваша строка - json, поэтому вы можете загрузить ее как python диктовку и просмотреть результаты.
import json
results = b'{"examination":"G.C.E. (O/L) EXAMINATION","year":"2018","name":"NANAYAKKARA IGALA ARACHCHIGE NAVINDU THARUKA PERERA","indexNo":"80299920","nic":null,"districtRank":null,"islandRank":null,"marks":null,"status":null,"zScore":null,"stream":null,"subjectResults":[{"subjectName":"BUDDHISM","subjectResult":"A"},{"subjectName":"SINHALA LANGUAGE & LITT.","subjectResult":"A"},{"subjectName":"ENGLISH LANGUAGE","subjectResult":"A"},{"subjectName":"MATHEMATICS","subjectResult":"A"},{"subjectName":"HISTORY","subjectResult":"A"},{"subjectName":"SCIENCE","subjectResult":"B"},{"subjectName":"DRAMA & THEATRE(SINHALA)","subjectResult":"A"},{"subjectName":"BUSINESS & ACCT. STUDIES","subjectResult":"A"},{"subjectName":"INFOR. & COMM. TECHNOLOGY","subjectResult":"A"}],"studentInfo":[{"param":"Examination","value":"G.C.E. (O/L) EXAMINATION"},{"param":"Year","value":"2018"},{"param":"Name","value":"NANAYAKKARA IGALA ARACHCHIGE NAVINDU THARUKA PERERA"},{"param":"Index Number","value":"80299920"},{"param":"NIC Number","value":""}]}'
result_dict = json.loads(results)
for subject in result_dict['subjectResults']:
print('Name: ', subject['subjectName'])
print('Result: ', subject['subjectResult'])
print()
# prints
"""
Name: BUDDHISM
Result: A
Name: SINHALA LANGUAGE & LITT.
Result: A
Name: ENGLISH LANGUAGE
Result: A
Name: MATHEMATICS
Result: A
Name: HISTORY
Result: A
Name: SCIENCE
Result: B
Name: DRAMA & THEATRE(SINHALA)
Result: A
Name: BUSINESS & ACCT. STUDIES
Result: A
Name: INFOR. & COMM. TECHNOLOGY
Result: A
"""