无法从 JSON 结果中检索值

Question

我正在使用 REST 调用从表中检索条目，方法是按属性搜索，将字节转换为字符串，然后从结果中获取 objectId 值。

new_requests = Popen(['curl',
                  '-H', 'application-id: %s' % backendless_appid,
                  '-H', 'secret-key: %s' % backendless_sk,
                  '-H', 'Content-Type: application/json',
                  '-X', 'GET',
                  '-v', 'https://api.backendless.com/v1/data/Request?where=requestId%3D1'],
                 stdout=PIPE).communicate()[0]

new_requests_str = new_requests.decode(encoding='utf-8')

new_requests_objectid = json.loads(new_requests_str, strict=False)['objectId']

不幸的是，这导致KeyError: 'objectId'

print(new_requests_str)返回JSON结果，所以问题是new_requests_objectid。

{"offset":0,"data":[{"emailAddress":"eric@apakau.com","apiEndpoint":"http://www.yahoo.com","created":1438986033000,"requestId":"1","___class":"Request","ownerId":null,"updated":1439222409000,"objectId":"723B5AEE-5D60-E00E-FF92-ACA3B4629F00","apiSecretkey":"asdfasa","__meta":"{\"relationRemovalIds\":{},\"selectedProperties\":[\"emailAddress\",\"apiEndpoint\",\"created\",\"requestId\",\"___class\",\"ownerId\",\"updated\",\"objectId\",\"apiSecretkey\"],\"relatedObjects\":{}}"}],"nextPage":null,"totalObjects":1}

Answer 1

objectId 不是 new_requests json 中的直接键。相反，它是data 列表中字典的一部分。所以你需要像那样访问它。请求最有可能返回包含多个对象（和多个 objectIds ）的响应，所以我建议将它们保存在一个列表中，示例 -

new_requests = Popen(['curl',
                  '-H', 'application-id: %s' % backendless_appid,
                  '-H', 'secret-key: %s' % backendless_sk,
                  '-H', 'Content-Type: application/json',
                  '-X', 'GET',
                  '-v', 'https://api.backendless.com/v1/data/Request?where=requestId%3D1'],
                 stdout=PIPE).communicate()[0]

new_requests_str = new_requests.decode(encoding='utf-8')

new_requests_objectIds = []

for data_item in json.loads(new_requests_str, strict=False)['data']:
    new_requests_objectIds.append(data_item['objectId'])