rate_limiter.py

import time

def rate_limiter(period, damping = 1.0):
  """
  Prevent a method from being called if it was previously called before
  a time widows has elapsed.
  :param period: The time window after which method invocations can continue
  :param damping: A factor by which to dampen the time window.
  :return function: Decorated function that will forward method invocations if the time window has elapsed.
  """
  frequency = damping / float(period)
  def decorate(func):
    last_time_called = [0.0]
    def rate_limited_function(*args, **kargs):
      elapsed = time.clock() - last_time_called[0]
      left_to_wait = frequency - elapsed
      if left_to_wait > 0:
        time.sleep(left_to_wait)
      ret = func(*args, **kargs)
      last_time_called[0] = time.clock()
      return ret
    return rate_limited_function
  return decorate

# Usage
# Assume we have rate limit below func , like max 10 call per second for that method
@rate_limiter(10)
def func(i):
    # do something here, which you want to rate limit it like third party apis
    # calling which have a very strict rules to send no of requests within a
    # given time frame (like, 10 requests per second)
    res = 'RESULT HERE'
    print 'Running %s' % i
    return res

if __name__ == "__main__":
    for i in range(0, 20):
        func(i)