Python: Convert a list of python dictionaries to an array of JSON objects

Question

I'm trying to write a function to convert a python list into a JSON array of {"mpn":"list_value"} objects, where "mpn" is the literal string value I need for every object but "list_value" is the value from the python list. I'll use the output of this function for an API get request.

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

def json_list(list):
    lst = []
    d = {}
    for pn in list:
        d['mpn']=pn
        lst.append(d)
    return json.dumps(lst, separators=(',',':'))

print json_list(part_nums)

This current function is not working and returns last value in the python list for all JSON objects:

>[{"mpn":"CC0402KRX5R8BB104"},{"mpn":"CC0402KRX5R8BB104"},{"mpn":"CC0402KRX5R8BB104"}]

However, of course I need my function to return the unique list values in the objects as such:

>[{"mpn":"ECA-1EHG102"},{"mpn":"CL05B103KB5NNNC"},{"mpn":"CC0402KRX5R8BB104"}]

Bottom line is I don't understand why this function isn't working. I expected I could append a dictionary with a single {key:value} pair to a python list and it wouldn't matter that all of the dictionaries have the same key because they would be independent. Thanks for your help.

Answer 1

As explained by others (in answers) you should create a new dictionary for each item on the list elsewhere you reference always the same dictionary

import json
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)

print

[{"mpn": "ECA-1EHG102"}, {"mpn": "CL05B103KB5NNNC"}, {"mpn": "CC0402KRX5R8BB104"}]