Walk Through a Python Script

Turck builds industrial sensors, and its QA team runs an automated pass or fail check against every sensor reading before a batch ships. You're handed this Python script during a QA engineering interview and asked to walk through it end to end.

import time

def run_sensor_checks(readings, thresholds, retries=[]):
    results = []

    for sensor_id, value in readings.items():
        threshold = thresholds.get(sensor_id, thresholds["default"])
        attempt = 0
        passed = False

        while attempt < 3:
            if value <= threshold:
                passed = True
                break
            attempt += 1
            time.sleep(0.1)
            retries.append(sensor_id)

        results.append({
            "sensor_id": sensor_id,
            "value": value,
            "threshold": threshold,
            "passed": passed,
            "attempts": attempt + 1
        })

    return results


def summarize(results):
    total = len(results)
    failed = [r for r in results if not r["passed"]]
    pass_rate = (total - len(failed)) / total * 100

    return {
        "total": total,
        "failed": len(failed),
        "pass_rate": round(pass_rate, 1)
    }

Explain what run_sensor_checks and summarize do, in the order they execute. As you walk through it, call out anything you would flag in a code review, including behavior that only shows up on repeated calls or on edge-case inputs, since that's exactly what a QA engineer is expected to catch before this ships.