My solution to the Priceonomics Summer 2012 puzzle

puzzle.py

import json
from itertools import groupby
from operator import itemgetter


def hour_func(x):
    # strip off hours and minutes
    return x['timestamp'][:-6]


raw_json = json.loads(open('readings_formatted.json', 'r').read())

# sort by location then by hour to enable grouping
inital_sorted = sorted(raw_json, key=hour_func)
data = sorted(inital_sorted, key=itemgetter('location'))

groups = {}
for k, g in groupby(data, itemgetter('location')):
    group = {}
    for kk, gg in groupby(g, hour_func):
        temps = [x["temperature"] for x in gg]
        group[kk] = sum(temps) / float(len(temps))
    groups[k] = group

a = groups["NRT"]["2012-06-15 13"]
b = groups["IAD"]["2012-06-16 14"]
c = groups["SFO"]["2012-06-17 13"]

print a, b, c