Token bucket rate limiter in Python (in-memory)

import time
import threading


class TokenBucket:
    def __init__(self, capacity, refill_rate, refill_interval=1.0):
        self.capacity = capacity
        self.tokens = capacity
        self.refill_rate = refill_rate
        self.refill_interval = refill_interval
        self.last_refill = time.monotonic()
        self.lock = threading.Lock()

    def _refill(self):
        now = time.monotonic()
        elapsed = now - self.last_refill
        if elapsed > 0:
            new_tokens = elapsed * self.refill_rate
            self.tokens = min(self.capacity, self.tokens + new_tokens)
            self.last_refill = now

    def consume(self, tokens=1):
        with self.lock:
            self._refill()
            if self.tokens >= tokens:
                self.tokens -= tokens
                return True
            return False


if __name__ == "__main__":
    bucket = TokenBucket(capacity=5, refill_rate=2)
    for _ in range(8):
        print(f"consume 1 -> {bucket.consume()}")
    time.sleep(1)
    print(f"after 1s refill -> {bucket.consume()}")