How to implement a tumbling window aggregation in Python

import time
from collections import deque

class TumblingWindow:
    def __init__(self, duration_seconds):
        self.duration = duration_seconds
        self.buffer = deque()
        self.window_start = None

    def add(self, item):
        current_time = time.time()
        if self.window_start is None:
            self.window_start = current_time

        if current_time - self.window_start >= self.duration:
            self.process_window()
            self.window_start = current_time
            self.buffer.clear()

        self.buffer.append(item)

    def process_window(self):
        if not self.buffer:
            return
        total = sum(self.buffer)
        count = len(self.buffer)
        avg = total / count
        print(f"Window [{self.window_start:.2f} - {time.time():.2f}]: "
              f"items={count}, sum={total:.2f}, avg={avg:.2f}")

if __name__ == "__main__":
    window = TumblingWindow(duration_seconds=3)
    # Simulate events arriving over time
    test_values = [10, 20, 30, 40, 50]  # 5 events
    times = [0.0, 0.8, 1.5, 3.5, 4.5]   # arrival offsets in seconds
    start = time.time()
    for value, offset in zip(test_values, times):
        while time.time() - start < offset:
            time.sleep(0.05)
        window.add(value)
        print(f"Added {value} at t={offset:.1f}s")
    # Final flush for last window
    time.sleep(3.2)
    window.process_window()
    if window.buffer:
        window.process_window()