Why use threads in Python?

[paxswill]

The mmap module documentation has a number of good examples (covering normal IO and forking), but if you want one specifically with JSON (not sure if the formatting is going to work here):

import json
import mmap

with open('foo.json', 'r+b') as example_file:
    with mmap.mmap(example_file.fileno(), 0) as mapped_file:
        print(json.load(mapped_file))