Python : Convert CSV to JSON (line by line)

convert_csv_to_json

def convertCSVtoJSON(input): #pass the name of the input csv file
	f = open(input, 'r')     
	j = open('.tempJSON', 'w')
	fieldnames = ("field1,field2,field3")
	reader = csv.DictReader(f, fieldnames)
	for row in reader:
		json.dump(row, j)
		j.write('\n')
	f.close()
	j.close()
	os.system('rm -f input')
	os.system('mv .tempJSON input')
	return
	
	#the output is a file in which every line is a JSON document