Can json.loads ignore trailing commas?

Strip the commas before you pass the value in.

import re

def clean_json(string):
    string = re.sub(",[ \t\r\n]+}", "}", string)
    string = re.sub(",[ \t\r\n]+\]", "]", string)

    return string

In python you can have trailing commas inside of dictionaries and lists, so we should be able to take advantage of this using ast.literal_eval:

import ast, json

str = '{"key1": "value1", "key2": "value2",}'

python_obj = ast.literal_eval(str) 
# python_obj is {'key1': 'value1', 'key2': 'value2'}

json_str = json.dumps(python_obj)
# json_str is '{"key1": "value1", "key2": "value2"}'

However, JSON isn't exactly python so there are a few edge cases to this. For example, values like null, true, false don't exist in python. We can replace those with valid python equivalents before we run the eval:

import ast, json

def clean_json(str):
  str = str.replace('null', 'None').replace('true', 'True').replace('false', 'False')
  return json.dumps(ast.literal_eval(str))

This will unfortunately mangle any strings that have the words null, true, or false in them.

{"sentence": "show your true colors"} 

would become

{"sentence": "show your True colors"}

You can wrap python's json parser with jsoncomment

JSON Comment allows to parse JSON files or strings with:

• Single and Multi line comments
• Multi line data strings
• Trailing commas in objects and arrays, after the last item

Example usage:

import json
from jsoncomment import JsonComment

with open(filename) as data_file:    
    parser = JsonComment(json)
    data = parser.load(data_file)

Fast forward to 2021, now we have https://pypi.org/project/json5/

A quote from the link:

A Python implementation of the JSON5 data format.

JSON5 extends the JSON data interchange format to make it slightly more usable as a configuration language:

• JavaScript-style comments (both single and multi-line) are legal.
• Object keys may be unquoted if they are legal ECMAScript identifiers
• Objects and arrays may end with trailing commas.
• Strings can be single-quoted, and multi-line string literals are allowed.

Usage is consistent with python's built in json module:

>>> import json5
>>> json5.loads('{"key1": "{my special value,}",}')
{u'key1': u'{my special value,}'}

It does come with a warning:

Known issues

• Did I mention that it is SLOW?

It is fast enough for loading start up config etc.