[Python] How to extract multiple JSON objects from one file?

I am very new to Json files. If I have a json file with multiple json objects such as following:

{"ID":"12345","Timestamp":"20140101", "Usefulness":"Yes",
"Code":[{"event1":"A","result":"1"},…]}
{"ID":"1A35B","Timestamp":"20140102", "Usefulness":"No",
"Code":[{"event1":"B","result":"1"},…]}
{"ID":"AA356","Timestamp":"20140103", "Usefulness":"No",
"Code":[{"event1":"B","result":"0"},…]}
…


I want to extract all "Timestamp" and "Usefulness" into a data frames:

Timestamp Usefulness
0 20140101 Yes
1 20140102 No
2 20140103 No
…


Does anyone know a general way to deal with such problems?

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