Convert python decimal to string in deeply nested and unpredictable list

Question

I am trying to loop through every value in a deeply nested/mixed list and convert any Decimal instances to string so that I can store them in mongo.

My attempt at re

Answer 1

To convert Decimal during json.dump() using default parameter:

import json
import sys
from decimal import Decimal

def default(obj):
    if isinstance(obj, Decimal):
        return str(obj)
    else:
        raise TypeError(obj)

# convert during dump
json.dump(data, sys.stdout, indent=2, default=default)

To modify data inplace:

import json
import sys
from collections import MutableMapping, MutableSequence
from decimal import Decimal

def convert_decimal(json_data):
    stack = [json_data]
    while stack:
        json_data = stack.pop()
        if isinstance(json_data, MutableMapping): # json object
            it = json_data.items()
        elif isinstance(json_data, MutableSequence): # json array
            it = enumerate(json_data)
        else: # scalar data
            continue

        for k, v in it:
            if isinstance(v, Decimal):
                json_data[k] = str(v)
            else:
                stack.append(v)


# convert inplace
convert_decimal(data)
json.dump(data, sys.stdout, indent=2)

Both scripts produce the same output:

[
  {
    "Payments": {
      "OtherFees": "0", 
      "APR": "2.54", 
      "Rate": "0.0254", 
      "IsCapped": true, 
      "Name": "TestData", 
      "Program": {
        "Description": null, 
        "ProgramName": "AST"
      }, 
      "AppliedIds": [], 
      "CapCostTotal": "27900", 
      "Tax": "0", 
      "Payment": "495.64"
    }
  }
]

You could simplify convert_decimal() if you use a generic get_items() function:

def convert_decimal(json_data):
    stack = [json_data]
    while stack:
        json_data = stack.pop()
        for k, v in get_items(json_data):
            if isinstance(v, Decimal):
                json_data[k] = str(v)
            else:
                stack.append(v)

Answer 2

You want to convert decimals to strings, but recursively apply your function to the contents of lists and the values of dictionaries, otherwise return objects unchanged? Then do that:

def strip_decimals(o):
    if type(o) == Decimal:
        return str(o)
    elif type(o) == list:
        return map(strip_decimals, o)
    elif type(o) == dict:
        return dict([(k, strip_decimals(v)) for k, v in o.iteritems()])
    else:
        return o

Results in:

[{'Payments': {'APR': '2.54',
           'AppliedIds': [],
           'CapCostTotal': '27900',
           'IsCapped': True,
           'Name': 'TestData',
           'OtherFees': '0',
           'Payment': '495.64',
           'Program': {'Description': None, 'ProgramName': u'AST'},
           'Rate': '0.0254',
           'Tax': '0'}}]