import json
string_data = '{"S.No":"9","data":[{"id":"ID1","value":" 0.34"},{"id":"ID2","value":" 2.92"},{"id":"ID3","value":" 2.92"}]}'
data = json.loads(string_data)
[float(d['value']) for d in data['data']]
# will result in:
[0.34, 2.92, 2.92]