如何在循环中过滤不同withdrawal分组下的重复deposit ID？

我有一个包含多个withdrawal分组的列表，每个分组下对应一组deposit数据。需要实现：同一deposit ID只能出现在第一个包含它的withdrawal分组中，后续分组要过滤掉已出现过的deposit。withdrawal分组数量不固定，可能多于2个。尝试过基于lambda的过滤方法，但没得到预期结果。

示例输入 #

exampleList = [
    {
      "withdrawal": {
        "amount": 250,
        "id": 70916631583,
        "date": "31-05-22 - 16:14:08",
        "paytype": "withdrawal"
      },
      "deposit": [
        {
          "id": 71018974368,
          "amount": 120,
          "date": "01-06-22 - 14:27:26",
          "paytype": "deposit"
        },
        {
          "id": 71018971332,
          "amount": 100,
          "date": "01-06-22 - 14:27:23",
          "paytype": "deposit"
        }
      ]
    },
    {
      "withdrawal": {
        "amount": 220,
        "id": 71019072820,
        "date": "01-06-22 - 14:28:40",
        "paytype": "withdrawal"
      },
      "deposit": [
        {
          "id": 71033338591,
          "amount": 100,
          "date": "01-06-22 - 17:03:19",
          "paytype": "deposit"
        },
        {
          "id": 71033144597,
          "amount": 250,
          "date": "01-06-22 - 17:01:20",
          "paytype": "deposit"
        },
        {
          "id": 71018974368,
          "amount": 120,
          "date": "01-06-22 - 14:27:26",
          "paytype": "deposit"
        },
        {
          "id": 71018971332,
          "amount": 100,
          "date": "01-06-22 - 14:27:23",
          "paytype": "deposit"
        }
      ]
    }
  ]

预期输出 #

exampleOutputList = [
    {
      "withdrawal": {
        "amount": 250,
        "id": 70916631583,
        "date": "31-05-22 - 16:14:08",
        "paytype": "withdrawal"
      },
      "deposit": [
        {
          "id": 71018974368,
          "amount": 120,
          "date": "01-06-22 - 14:27:26",
          "paytype": "deposit"
        },
        {
          "id": 71018971332,
          "amount": 100,
          "date": "01-06-22 - 14:27:23",
          "paytype": "deposit"
        }
      ]
    },
    {
      "withdrawal": {
        "amount": 220,
        "id": 71019072820,
        "date": "01-06-22 - 14:28:40",
        "paytype": "withdrawal"
      },
      "deposit": [
        {
          "id": 71033338591,
          "amount": 100,
          "date": "01-06-22 - 17:03:19",
          "paytype": "deposit"
        },
        {
          "id": 71033144597,
          "amount": 250,
          "date": "01-06-22 - 17:01:20",
          "paytype": "deposit"
        }
        
      ]
    }
  ]

尝试过的代码及问题 #

之前尝试用循环记录已出现的ID，但逻辑错误，导致输出仍有重复ID：

listLen = len(exampleList)
testList = []
if(listLen > 0):
    while listLen > 0:
        listLen -= 1
        deposits = exampleList[listLen]['deposit']
        withDrawal = exampleList[listLen]['withdrawal']
        idList = [x['id'] for x in deposits]
        filterFromList = list(filter(lambda x:x['id'] not in testList, deposits))
        testList.append({"withdrawal" : withDrawal,"deposit" : filterFromList})
        
    print(testList)

输出结果里重复的deposit ID依然存在，因为testList存储的是整个分组对象，而非已出现的deposit ID集合，过滤条件完全不生效。

解决方案 #

核心是用一个集合来记录已经出现过的deposit ID，然后正序遍历每个withdrawal分组，过滤掉当前分组中已存在于集合的deposit，同时将新的deposit ID加入集合。

seen_deposit_ids = set()
result = []

for group in exampleList:
    # 过滤当前分组中未出现过的deposit
    filtered_deposits = [d for d in group['deposit'] if d['id'] not in seen_deposit_ids]
    # 将当前分组中保留的deposit ID加入已见集合
    seen_deposit_ids.update(d['id'] for d in filtered_deposits)
    # 构建结果分组
    result.append({
        "withdrawal": group['withdrawal'],
        "deposit": filtered_deposits
    })

# 打印格式化后的结果
import json
print(json.dumps(result, indent=2))

代码说明 #

1. seen_deposit_ids是一个集合，用于快速判断ID是否已出现（集合的in操作时间复杂度为O(1)，比列表高效）。
2. 正序遍历原列表，确保第一个出现的deposit ID被保留在对应的分组中。
3. 过滤后，将当前分组保留的deposit ID全部加入集合，后续分组会自动过滤这些ID。
4. 最后用json.dumps格式化输出，方便查看结构。

运行这段代码后，就能得到符合预期的输出：每个deposit ID仅出现在第一个包含它的withdrawal分组中，后续分组不会重复出现。

内容的提问来源于stack exchange，提问作者Ozans