通过字典列表的键重新编码值

Question

I have a json object that is a list of dictionaries, that comes from an api. I'm looking for changing the values of certain keys of the json before inserting them into a database. The list looks like this:

[
  {
    'id': 1,
    'sex': 'Female'
    'status': 'Active'
  },
  {...},
]

The json always have all keys presented. I want to change the string values of the keys for integers, since it would fit the database model:

[
  {
    'id': 1,
    'sex': 2
    'status': 1
  },
  {...},
]

I'm capable of changing one dictionary item using .update('key': recode_fun) or iterate through the whole list, but I don't see how to do both without several loops (loop through the range, list and dictionary). I'm trying to do it using a helper function:

def recode_sex(value):
    return {
      'Male': 1,
      'Female': 2,
    }.get(value, value)

Since there are multiple keys value that needs updated and want to keep the loops readable.

Answer 1

You do not want a list of dictionaries but a dictionary of dictionaries. Something like:

code_table = {
  'sex':
    {'Male': 1,
     'Female': 2
    },
  'status':
    {'Active': ...
    },
  ...
}

You can then build the recoded list with a simple comprehension:

recoded = [{k: code_table.get(k, {v: v})[v] for k,v in d.items()} for d in data]

Answer 2

If you already have the helper functions then you only need to loop once through each item of the list and modify all your key:value pairs:

for i in list:
    i['key'] = recode_key(i['key'])
    i['anotherkey'] = recode_anotherkey(i['key'])
    i['yetanotherkey'] = recode_yetanotherkey(i['key'])

You would need to loop through the list once, touch all the keys that you need, and your helper function makes sure that you don't update the key twice or with another value.