could also just use pandas
import sys
import pandas as pd
infile = sys.argv[1]
df = pd.read_json(infile)
# flattened json could also be done
#import json
#data_dict = json.load(open(infile))
#df = pd.json_normalize(data_dict)
df.to_csv(infile.replace('.json','.csv'), index=False)