Implement circuit breaker open after failures demo in Python

import time
from datetime import datetime


class CircuitBreaker:
    def __init__(self, threshold=3):
        self.threshold = threshold
        self.failure_count = 0
        self.is_open = False

    def call(self, func, *args, **kwargs):
        if self.is_open:
            raise RuntimeError("Circuit is OPEN")
        try:
            result = func(*args, **kwargs)
            self.failure_count = 0
            return result
        except Exception as e:
            self.failure_count += 1
            if self.failure_count >= self.threshold:
                self.is_open = True
            raise e


def flaky_service():
    print(f"  [{datetime.now().strftime('%H:%M:%S')}] flaky_service called")
    raise ConnectionError("Service unavailable")


if __name__ == "__main__":
    circuit = CircuitBreaker(threshold=3)
    for i in range(5):
        try:
            circuit.call(flaky_service)
        except (ConnectionError, RuntimeError) as e:
            print(f"  attempt {i+1}: {type(e).__name__}: {e}")
    print(f"\nCircuit open: {circuit.is_open}")
    print("Sample demonstrates circuit breakers stop calling failing services after threshold")