Python snippet that throttles a function call. This is useful when the function request a remote service that having throttling policy. We must honor the throttling, otherwise we will be banned.

throttled_call.py

import time
from collections import deque

def throttled_call(func, args=(), kwargs={}, threshold_per_minute=60):
    """Throttling the function call with ``threshold_per_minute`` calls per minute. 

    This is useful when the function request a remote service that having throttling policy. 
    We must honor the throttling, otherwise we will be banned.

    :param func: the function to be called
    :param args: args of that function
    :param kwargs: kwargs of that function
    :param threshold_per_minute: defines how many calls can be made to the function per minute 

    Example Usage::
    
    >>> import time
    >>> def print_hello():
    ...     print 'hello'

    and calling the following will make the ``print_hello`` function less annoying
    >>> while True:
    >>>     throttled_call(print_hello, threshold_per_minute=60)
    """
    if not hasattr(throttled_call, 'logs'):
        throttled_call.logs = deque()
    logs = throttled_call.logs

    def remove_outdated():
        # remove outdated from logs
        t = time.time()
        while True:
            if logs and logs[0] < t - 60:
                logs.popleft()
            else:
                break

    def wait_for_threshold():
        while len(logs) > threshold_per_minute:
            remove_outdated()
            time.sleep(0.3)

    def smoothen_calling_interval():
        average_processing_time = (time.time() - logs[0]) / len(logs)
        expected_processing_time = 60. / threshold_per_minute
        if expected_processing_time > average_processing_time:
            time.sleep((len(logs)+0.8)*expected_processing_time - len(logs)*average_processing_time)

    if logs and len(logs) < threshold_per_minute:
        smoothen_calling_interval()
    else:
        wait_for_threshold()

    logs.append(time.time())

    return func(*args, **kwargs)


def test_hello():
    def print_hello():
        print 'hello'

    while True:
        throttled_call(print_hello, threshold_per_minute=60)

if __name__ == '__main__':
    test_hello()