part_nums = ['ECA-1EHG102', 'CL05B103KB5NNNC', 'CC0402KRX5R8BB104']

def json_list(list):
    lst = []
for pn in list:
    d = {}
d['mpn'] = pn
lst.append(d)
return json.dumps(lst)
print(json_list(part_nums))
Python: Convert a list of python dictionaries to an array of JSON objects