Generic decorator to handle multiple rate limits in API calls

ratelimiting.py

import sys, time
from collections import deque

_DEFAULT_POLICY = {1:1}

def rate_limited(*args):
	"""
	policy is an object where each key is a time interval in seconds and each value is a maximum number of requests during this interval.
		{1:1} means 1 request max per second
		{1:5} means 5 requests max per second
		{1:2,60:60,3600:1800} means 1800 requests max per hour, 60 requests max per minute, 2 requests max per second
	"""
	def decorator(f):
		def wrapper(*args, **kwargs):
			if len(RATE_LIMITS) > 0:
				now = time.time()
				N = len(RATE_LIMITS)
				timestamps = [now - x[0] for x in RATE_LIMITS]
				indexes = [None] * N
				counts = [0] * N
				while len(TIMESTAMPS):
					if TIMESTAMPS[0] < timestamps[0]:
						TIMESTAMPS.popleft()
					else:
						break
				for n, t in enumerate(TIMESTAMPS):
					for i in range(N):
						if t >= timestamps[i]:
							if indexes[i] is None:
								indexes[i] = n
							counts[i] += 1
						else:
							break
				delay = 0.
				for i in range(N):
					if indexes[i] is None:
						break
					if counts[i] >= RATE_LIMITS[i][1]:
						delay = max(delay, TIMESTAMPS[indexes[i] + counts[i] - RATE_LIMITS[i][1]] - timestamps[i])
				if delay > 0:
					sys.stderr.write("%s waiting %.1fs\n" % (f, delay))
					time.sleep(delay)
				TIMESTAMPS.append(time.time())
			return f(*args, **kwargs)
		return wrapper
	TIMESTAMPS = deque([])
	if len(args) == 1 and callable(args[0]):
		policy = __DEFAULT_POLICY
		_decorator = decorator(args[0])
	else:
		if len(args):
			policy = args[0]
		else:
			policy = __DEFAULT_POLICY
		_decorator = decorator
	RATE_LIMITS = sorted([(a, b) for (a, b) in policy.items() if min(a, b) > 0], reverse=True)
	return _decorator

if __name__ == '__main__':
	from threading import Thread
	@rate_limited({1:3, 5:7, 10:11})
	def f(n):
		return "f(%d) done" % n

	@rate_limited({1:5, 2:7, 3:11})
	def g(n):
		return "g(%d) done" % n

	def run(f):
		for i in range(20):
			print(f(i))
	t1 = Thread(target=run, args=(f,))
	t2 = Thread(target=run, args=(g,))
	t1.start()
	t2.start()