限速python装饰器

Question

我发现这个基于redis类的限速python装饰器.我怎样才能编写一个类似的装饰器,它只使用标准库中可用的内容,如下所示？

def ratelimit(limit, every):
    #  python magic 

@ratelimit(limit=1, every=2)
def printlimited(x):
    print x

# print one number every two seconds
for x in range(10):
    printlimited(x)

stackoverflow 还有其他答案,但它们不允许指定分母.

Answer 1

您可以使用a threading.Semaphore来计算和阻止超出限制的请求,并结合使用threading.Timer来计划释放信号量的函数.

from threading import Semaphore, Timer
from functools import wraps

def ratelimit(limit, every):
    def limitdecorator(fn):
        semaphore = Semaphore(limit)
        @wraps(fn)
        def wrapper(*args, **kwargs):
            semaphore.acquire()
            try:
                return fn(*args, **kwargs)
            finally:                    # don't catch but ensure semaphore release
                timer = Timer(every, semaphore.release)
                timer.setDaemon(True)   # allows the timer to be canceled on exit
                timer.start()
        return wrapper
    return limitdecorator