Python循环处理JSON遇KeyError如何补空而非跳过整个条目？

我正在循环处理包含客户信息的JSON文件，目的是将信息重新格式化为指定结构并生成新的JSON文件。但不同使用者运行脚本时，原始JSON文件有时会缺失字段。我希望程序遇到缺失字段时，将该字段填充为空字符串，继续处理其他存在的字段，而非跳过整个条目。

我编写的循环代码如下：

data = json.load(open('raw_data.json', 'r'))
customer_model = []

for row in data:
    try:
        customer_model.append({"RequestID": row['request_id'],
                               "Timestamp": n1 + "Z",
                               "ExternalID": row['external_id'],
                               "Fields": {
                                   "forename": row['forename'],
                                   "middle_name_1": row['middle_name_1'],
                                   "middle_name_2": row['middle_name_2'],
                                   "surname": row['surname'],
                                   "email": row['email'],
                                   "date_of_birth": row['date_of_birth'],
                                   "home_phone_number": row['home_phone_number'],
                                   "mobile_phone_number": row['mobile_phone_number'],
                                   "passport_number": str(row['passport_number']),
                                   "driving_licence": str(row['driving_licence']),
                               },
                               "Match": row['match']})
    except KeyError:
        ""
        continue

with open("customers.json", "w") as f:
    json.dump(customer_model, f, indent=4)

但这段代码会生成空的customers.json文件，移除try/except块则会在原始JSON缺失字段时触发KeyError。请问我哪里出错了？

补充：我希望当原始JSON缺失字段时，customers.json的输出示例如下：

[
    {
        "RequestID": "",
        "Timestamp": "2022-08-27T07:59:30.34Z",
        "ExternalID": "18e452a7-29e5-4ad3-baeb-f439e48f4d0c",
        "Fields": {
            "forename": "Vennie",
            "middle_name_1": "Takisha",
            "middle_name_2": "Ebonie",
            "surname": "Castro",
            "email": "bemar1973@yandex.com",
            "date_of_birth": "",
            "home_phone_number": "016977 0528",
            "mobile_phone_number": "056 5567 8799",
            "passport_number": "",
            "driving_licence": "",
        },
        "Match": false
    }
]

错误原因 #

代码的核心问题在于try/except的逻辑：只要任意一个字段缺失触发KeyError，就会执行continue直接跳过整个客户条目，不会将其加入customer_model列表。如果所有条目都存在缺失字段，最终生成的文件自然是空的。另外，except块里的空字符串没有实际作用。

修改方案 #

放弃对整个条目构建逻辑加try/except，改用字典的get()方法处理每个字段——get(key, 默认值)会在键不存在时返回指定默认值（此处用空字符串），彻底避免触发KeyError。

对于需要转字符串的字段（如passport_number、driving_licence），先通过get获取值（缺失时为空字符串）再转字符串，避免将None转换成"None"的无效内容。

修改后的代码如下：

import json

# 假设n1是已定义的时间字符串，示例值与输出示例匹配
n1 = "2022-08-27T07:59:30.34"

data = json.load(open('raw_data.json', 'r'))
customer_model = []

for row in data:
    customer_entry = {
        "RequestID": row.get('request_id', ''),
        "Timestamp": n1 + "Z",
        "ExternalID": row.get('external_id', ''),
        "Fields": {
            "forename": row.get('forename', ''),
            "middle_name_1": row.get('middle_name_1', ''),
            "middle_name_2": row.get('middle_name_2', ''),
            "surname": row.get('surname', ''),
            "email": row.get('email', ''),
            "date_of_birth": row.get('date_of_birth', ''),
            "home_phone_number": row.get('home_phone_number', ''),
            "mobile_phone_number": row.get('mobile_phone_number', ''),
            "passport_number": str(row.get('passport_number', '')),
            "driving_licence": str(row.get('driving_licence', '')),
        },
        "Match": row.get('match', False)
    }
    customer_model.append(customer_entry)

with open("customers.json", "w") as f:
    json.dump(customer_model, f, indent=4)

代码说明 #

1. 所有字段通过row.get(字段名, '')获取，缺失时自动填充空字符串，无KeyError风险
2. passport_number和driving_licence先获取默认空字符串再转格式，避免生成"None"无效内容
3. Match字段默认设为False，与示例输出逻辑一致
4. 移除原有的try/except和continue，确保每个条目都会被处理并加入结果列表

内容的提问来源于stack exchange，提问作者nocnoc