Duplicated json keys

duplicates.py

#!/usr/bin/env python

import json
import sys


def list_duplicates(seq):
    seen = set()
    seen_add = seen.add
    # adds all elements it doesn't know yet to seen and all other to seen_twice
    seen_twice = set( x for x in seq if x in seen or seen_add(x) )
    # turn the set into a list (as requested)
    return list( seen_twice )


def conflict(arg):
    keys = map(lambda x: x[0], arg)
    dups = list_duplicates(keys)
    if dups:
        print dups
    return arg


content = open(sys.argv[1]).read()
json.loads(content, object_pairs_hook=conflict)