Python读取JSON触发KeyError，如何修复获取totalQuantity的问题

问题详情 #

原代码 #

with open('C:/asg/response2.json') as json_file:
    data2 = json.load(json_file)

if 'priceResponse' in data2:    
    item = data2['priceResponse']['PriceAvailabilityList'][0]
    property_valuesa.append(item['totalQuantity'])
    property_values2a.append(item['PriceAvailabilityList']['price'])
    
print (property_valuesa)
input ("key enter")

报错信息 #

property_valuesa.append(item['totalQuantity'])
KeyError: 'totalQuantity'

读取的JSON示例 #

{
    "priceResponse": {
        "customerNo": "2312312",
        "userName": "23131@er.com",
        "PriceAvailabilityList": [
            {
                "sku": "12133223",
                "mfgPN": "DELL-sdad",
                "status": "Not authorized to buy",
                "GlobalProductStatusCode": "Not authorized to buy",
                "lineNumber": "1"
            },
            {
                "sku": "38384774",
                "mfgPN": "DELL-E322323H",
                "mfgCode": "23232",
                "status": "Active",
                "description": "27 MON 323232",
                "GlobalProductStatusCode": "Active",
                "price": "195.72",
                "totalQuantity": "138",
                "AvailabilityByWarehouse": [
                    {
                        "warehouseInfo": {
                            "number": "123",
                            "zipcode": "23344",
                            "city": "test, TT",
                            "addr": "testaddress"
                        },
                        "qty": "0"
                    },
                    {
                        "warehouseInfo": {
                            "number": "123",
                            "zipcode": "2344",
                            "city": "TEST, TT",
                            "addr": "testaddress Drive"
                        },
                        "qty": "0"
                    },
                    {
                        "warehouseInfo": {
                            "number": "233",
                            "zipcode": "213",
                            "city": "TEST, te",
                            "addr": "testaddress Pkwy"
                        },
                        "qty": "138"
                    },
                    {
                        "warehouseInfo": {
                            "number": "243",
                            "zipcode": "34324",
                            "city": "test, tets",
                            "addr": "test Way"
                        },
                        "qty": "0"
                    },
                    {
                        "warehouseInfo": {
                            "number": "2312",
                            "zipcode": "2312",
                            "city": "test, TS",
                            "addr": "test"
                        },
                        "qty": "0"
                    }
                ],
                "lineNumber": "1"
            }
        ]
    }
}

错误原因 #

1. 索引取值错误：你直接取了PriceAvailabilityList数组的第0个元素，但该元素没有totalQuantity字段，这个字段实际在数组的第1个元素（索引为1）中。
2. 字段路径错误：item['PriceAvailabilityList']['price']逻辑错误，item本身就是PriceAvailabilityList的子元素，不存在嵌套的PriceAvailabilityList字段，price是item的直接属性。
3. 缺少字段存在判断：未检查目标字段是否存在，一旦元素缺少对应字段就会触发KeyError。

修复后的代码 #

方案1：取指定索引的目标元素 #

如果只需要获取第1个元素的totalQuantity和price，可以这样修改：

# 先初始化存储列表
property_valuesa = []
property_values2a = []

with open('C:/asg/response2.json') as json_file:
    data2 = json.load(json_file)

if 'priceResponse' in data2:    
    # 取数组的第1个元素（索引为1）
    item = data2['priceResponse']['PriceAvailabilityList'][1]
    # 先判断字段存在再取值，避免报错
    if 'totalQuantity' in item:
        property_valuesa.append(item['totalQuantity'])
    if 'price' in item:
        property_values2a.append(item['price'])
    
print(property_valuesa)
print(property_values2a)
input("按回车退出")

方案2：遍历所有元素收集有效数据 #

如果需要收集数组中所有包含totalQuantity和price的元素数据，推荐用遍历方式：

property_valuesa = []
property_values2a = []

with open('C:/asg/response2.json') as json_file:
    data2 = json.load(json_file)

if 'priceResponse' in data2 and 'PriceAvailabilityList' in data2['priceResponse']:
    # 遍历数组中所有元素
    for item in data2['priceResponse']['PriceAvailabilityList']:
        # 只处理同时存在两个目标字段的元素
        if 'totalQuantity' in item and 'price' in item:
            property_valuesa.append(item['totalQuantity'])
            property_values2a.append(item['price'])
    
print(property_valuesa)
print(property_values2a)
input("按回车退出")

补充说明 #

• 处理JSON数据时，永远不要默认字段一定存在，务必加存在性判断，避免KeyError。
• 也可以用get方法简化判断，比如item.get('totalQuantity')，字段不存在时会返回None而非报错。

内容的提问来源于stack exchange，提问作者alex1290