Rate limiting function calls with Python Decorators

rateLimitDecorator.py

import time

def RateLimited(maxPerSecond):
    minInterval = 1.0 / float(maxPerSecond)
    def decorate(func):
        lastTimeCalled = [0.0]
        def rateLimitedFunction(*args,**kargs):
            elapsed = time.clock() - lastTimeCalled[0]
            leftToWait = minInterval - elapsed
            if leftToWait>0:
                time.sleep(leftToWait)
            ret = func(*args,**kargs)
            lastTimeCalled[0] = time.clock()
            return ret
        return rateLimitedFunction
    return decorate

@RateLimited(2)  # 2 per second at most
def PrintNumber(num):
    print num

if __name__ == "__main__":
    print "This should print 1,2,3... at about 2 per second."
    for i in range(1,100):
        PrintNumber(i)

An extended version of @oPromessa 's utility. Thank you for sharing @oPromessa !

I added Python 3.12 generic type-hinting and support for recursive calls using an RLock:

from typing import Callable, cast
from functools import wraps
import threading
import time


def rate_limited[T, **P](max_per_second: int) -> Callable[[Callable[P, T]], Callable[P, T]]:

    def decorator(fn: Callable[P, T]) -> Callable[P, T]:

        lock = threading.RLock()
        min_interval = 1.0 / max_per_second
        last_time_called = 0.0

        @wraps(fn)
        def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
            with lock:
                nonlocal last_time_called
                elapsed = time.perf_counter() - last_time_called
                left_to_wait = min_interval - elapsed
                if left_to_wait > 0:
                    time.sleep(left_to_wait)

                last_time_called = time.perf_counter()
                return fn(*args, **kwargs)

        return cast(Callable[P, T], wrapper)

    return decorator