import time
[docs]class RateLimit:
'''
A RateLimit class may be used to detect/enforce rate limits.
Example:
# allow 20 uses per 10 sec ( 2/sec )
rlimit = RateLimit(20,10)
Notes:
It is best ( even in a "calls per day" type config ) to
specify a smaller "per" to force rate "smoothing".
'''
def __init__(self, rate, per):
self.rate = float(rate)
self.per = float(per)
self.lasttick = time.time()
self.allowance = float(rate)
self.persec = float(rate) / float(per)
self.onetick = float(per) / float(rate)
[docs] def allows(self):
'''
Returns True if the rate limit has not been reached.
Example:
if not rlimit.allows():
rasie RateExceeded()
# ok to go...
'''
tick = time.time()
passed = tick - self.lasttick
self.allowance = min(self.rate, self.allowance + (passed * self.persec))
self.lasttick = tick
if self.allowance < 1.0:
return False
self.allowance -= 1.0
return True