Recurly.js signature implementation in Python

gistfile1.py

import hashlib
import hmac

def digest_data(data):
    if type(data) == list:
        return "[%s]" % (",".join([digest_data(v) for v in data if v]))
    elif type(data) == dict:
        kvs = sorted(data.items(), lambda x,y: cmp(x[0],y[0]))
        def prefix(key):
            return "" if type(key) == int else "%s:" % key
        kvs = ["%s%s" % (prefix(item[0]), digest_data(item[1])) for item in kvs if item[1]]
        return "[%s]" % ",".join(kvs)
    elif type(data) == str or type(data) == unicode:
        return "".join(map(lambda x: "\\"+x if x in "\\[]:," else x, data))
    else:
        return str(data)

def generate_signature(claim, args, timestamp, private_key):
    key = hashlib.sha1(private_key).digest()
    msg = digest_data([timestamp,claim,args])

    h = hmac.new(key, digestmod=hashlib.sha1)
    h.update(msg)
    return h.hexdigest() + "-" + str(timestamp)


test_sig = 'fb5194a51aa97996cdb995a89064764c5c1bfd93-1312806801'
key = "0123456789abcdef0123456789abcdef"
args = {"a":"foo", "b":"bar"}
assert generate_signature("update", args, 1312806801, key) == test_sig

assert digest_data({"a":1, "c":3, "b":2}) == '[a:1,b:2,c:3]'

assert digest_data({1:4, 2:5, 3:6}) == '[4,5,6]'

assert digest_data({"a":[1,2,3], "b":{"c": '123', "d":'456'}}) == '[a:[1,2,3],b:[c:123,d:456]]'

assert digest_data([[], {}, '', None]) == '[]'

assert digest_data({"syntaxchars":' \\ [ ] : , '}) == '[syntaxchars: \\\\ \[ \] \: \, ]'