simplest rate limiting algorithm in python

limit.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Ref. https://stackoverflow.com/questions/667508/whats-a-good-rate-limiting-algorithm#answer-668327

import time


def limit(rate, burst=0.0):
    unit = 1.0
    while rate < 1.0:
        rate *= 10
        unit *= 10
    mem = dict(
        last = time.time(),
        allowance = burst
    )
    def wrap():
        cur = time.time()
        elapsed = cur - mem['last']
        mem['last'] = cur
        mem['allowance'] += elapsed * rate / unit
        if mem['allowance'] > rate:
            mem['allowance'] = rate
        if mem['allowance'] < 1.0:
            return False
        else:
            mem['allowance'] -= 1.0
            return True
    return wrap