JSON-ification and processing of data with Python
It's slow because of this line:


for line in lines: 
    records = [item['hash'] for item in lines]



Notice that records will be overwritten for each line.
And in fact it's overwritten with the exact same value for each line.
In fact you could replace this loop with just this line:

records = [item['hash'] for item in lines]


That should already solve the problem with the slowness.
But I would go one step further and get records in one step,
by getting hash directly during the first pass over the input lines:

with open('toy.json', 'rb') as input:
    records = [json.loads(line)['hash'] for line in input]

    for item in records: 
        print item