How to Implement a Rate Limiter in Python

import time
from collections import deque


class RateLimiter:
    """Simple rate limiter for beginners."""

    def __init__(self, max_calls: int, period_seconds: float):
        self.max_calls = max_calls
        self.period = period_seconds
        self.calls = deque()

    def allow(self) -> bool:
        """Return True if a call is allowed, False otherwise."""
        now = time.monotonic()
        while self.calls and now - self.calls[0] >= self.period:
            self.calls.popleft()
        if len(self.calls) < self.max_calls:
            self.calls.append(now)
            return True
        return False


if __name__ == "__main__":
    limiter = RateLimiter(max_calls=3, period_seconds=1.0)

    for i in range(5):
        print(f"Call {i + 1}: {'allowed' if limiter.allow() else 'blocked'}")
    time.sleep(1.0)
    print("After 1 second:")
    print(f"Call 6: {'allowed' if limiter.allow() else 'blocked'}")