如何从JSON响应获取2个匹配结果后终止for循环并赋值变量

该需求完全可实现，且实现逻辑简单，还可以做到匹配到足够数量的结果后立刻终止遍历，避免全量扫描数据带来的不必要性能损耗。

• 变量名不统一：JSON加载后赋值给data变量，列表推导式中却调用了未定义的response变量，运行会直接抛NameError
• 类型调用错误：JSON反序列化后SnapshotCreateTime是字符串类型，直接调用时间对象专属的.strftime()方法会抛AttributeError
• 遍历逻辑缺陷：用列表推导式做筛选会遍历完所有快照数据，无法在匹配到2个结果后提前终止
• 变量设计不合理：尝试动态声明N个变量存储结果完全没必要，固定最多取2个结果的场景下，用列表收集结果后按长度解包即可，代码可维护性更高

import json
import sys

lookup_dt = "2022-03-09"

r = '{"DBClusterSnapshots": [{"DBClusterSnapshotIdentifier": "snap-1", "DBClusterIdentifier": "aurora-cluster", "SnapshotCreateTime": "2022-03-09T03:12:45.123Z", "Engine": "aurora-postgresql", "EngineVersion": "12.7", "SnapshotType": "manual"}, {"DBClusterSnapshotIdentifier": "snap-2", "DBClusterIdentifier": "aurora-cluster", "SnapshotCreateTime": "2022-03-09T08:45:12.456Z", "Engine": "aurora-postgresql", "EngineVersion": "12.7", "SnapshotType": "manual"}, {"DBClusterSnapshotIdentifier": "snap-3", "DBClusterIdentifier": "aurora-cluster", "SnapshotCreateTime": "2022-03-09T11:22:33.789Z", "Engine": "aurora-postgresql", "EngineVersion": "12.7", "SnapshotType": "manual"}]}'

data = json.loads(r)
matched_snaps = []

# 遍历快照列表，匹配到2个结果直接终止循环
for snap_item in data["DBClusterSnapshots"]:
    # 兼容带毫秒、时区的ISO时间格式，前10位固定为YYYY-MM-DD格式日期，无需转时间对象
    snap_date = snap_item["SnapshotCreateTime"][:10]
    if snap_date == lookup_dt:
        matched_snaps.append(snap_item["DBClusterSnapshotIdentifier"])
        # 凑够2个结果立刻跳出循环，不再遍历后续数据
        if len(matched_snaps) >= 2:
            break

# 按匹配结果数量走对应逻辑
if len(matched_snaps) == 0:
    print(f"ERROR: Snapshot did not find for requested date : {lookup_dt}")
    sys.exit(1)
elif len(matched_snaps) == 1:
    SnapshotId = matched_snaps[0]
    print(f"INFO: Found manual snapshots for requested date: {SnapshotId}")
else:
    SnapshotId, SnapshotId2 = matched_snaps
    print(f"INFO: Found manual snapshots for requested date: {SnapshotId}, {SnapshotId2}")

• 日期匹配做了格式兼容：不管接口返回的是纯日期字符串，还是带毫秒、时区的ISO格式时间戳，字符串前10位固定为YYYY-MM-DD格式，直接和目标日期比对即可，不需要做时间类型转换，性能更高也不会触发类型错误
• 遍历过程中每匹配到一个符合条件的快照ID就存入结果列表，当列表长度达到2时立刻执行break终止循环，后续的快照数据不会再被遍历
• 结果分支完全匹配需求：
  • 无匹配结果：打印错误日志，以状态码1退出程序
  • 匹配到1个结果：赋值给单个SnapshotId变量，打印对应提示
  • 匹配到2个及以上结果：只保留最先匹配到的前2个，解包赋值给SnapshotId和SnapshotId2两个变量，打印对应提示

内容的提问来源于stack exchange，提问作者Rj_N