Edit:
The data you provided is a JSON string. You can convert it to a dictionary using the json package:
import json
payload = u'{"encrypted_sender_transaction_id":"514658451",...}'
obj = json.loads(payload)
print obj['donation_info']['amount']
# 1
obj is a nested dictionary in this case, amount is a key in the subdictionary under the key donation_info
2
solved How to extract a field from this payload with a regex? [duplicate]