如何从一个时期中提取一天中的某小时，并对该小时内发生的每个实例进行计数？

import datetime

def count_instances_by_hour(records, target_hour):
    count = 0
    for record in records:
        # 提取记录的时间信息
        timestamp = record["timestamp"]
        record_time = datetime.datetime.fromtimestamp(timestamp)
        
        # 检查记录是否在目标小时内
        if record_time.hour == target_hour:
            count += 1
    
    return count

# 假设有一组记录，每个记录包含时间戳字段"timestamp"
records = [
    {"timestamp": 1635447600},  # 2021-10-29 00:00:00
    {"timestamp": 1635451200},  # 2021-10-29 01:00:00
    {"timestamp": 1635454800},  # 2021-10-29 02:00:00
    {"timestamp": 1635458400},  # 2021-10-29 03:00:00
    # ...
]

target_hour = 2
hourly_count = count_instances_by_hour(records, target_hour)
print(f"在{target_hour}点发生的实例数量为: {hourly_count}")