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解析json时的python else

json python

Milister · 技术社区 · 6 年前

有时(不经常)下面的json有额外的字段之间 EventName 和 EventSources 打电话 Username .

例如:

"EventName": "AssumeRole",
"EventSource": "sts.amazonaws.com",
"Username": "someuser"

有时它不会(如下所示)

我想创建if-else,所以if "Username": "someuser" 有没有,打印一个输出,如果没有,打印另一个。

with open('1.json') as file:
 data = json.load(file)

with open('cloudtrail.csv', 'wt') as file:
 #file.write('ResourceType,ResourceName,EventName,UserName\n')
 for element in data['Events']:
  if element['Username']:
   for resource in element['Resources']:
    print(resource['ResourceType'] + ',' + resource['ResourceName'] + ',' + element['EventName'] + ',' + element['Username'])
  else:
    print(resource['ResourceType'] + ',' + resource['ResourceName'] + ',' + element['EventName'])

但面对这个(因为 element['Username'] 不存在):

File "./cloud.py", line 24, in <module>
    if element['Username']:
KeyError: 'Username'

显然,我的假设逻辑出了问题

{
    "Events": [
        {
            "EventId": "62c8bac9-c486-4e1e-9603-58d8ba4a20f4",
            "EventTime": 1529020719.0,
            "CloudTrailEvent": "{\"eventVersion\":\"1.05\",\"userIdentity\":{\"type\":\"AWSService\",\"invokedBy\":\"vpc-flow-logs.amazonaws.com\"},\"eventTime\":\"2018-06-14T23:58:39Z\",\"eventSource\":\"sts.amazonaws.com\",\"eventName\":\"AssumeRole\",\"awsRegion\":\"us-east-1\",\"sourceIPAddress\":\"vpc-flow-logs.amazonaws.com\",\"userAgent\":\"vpc-flow-logs.amazonaws.com\",\"requestParameters\":{\"roleArn\":\"arn:aws:iam::279052847476:role/flowlogsRole\",\"roleSessionName\":\"vpc-flow-logging+279052847476\",\"externalId\":\"vpc-flow-logging+279052847476\",\"durationSeconds\":3600},\"responseElements\":{\"credentials\":{\"accessKeyId\":\"ASIAIOD3JIGRTBSRNP7A\",\"expiration\":\"Jun 15, 2018 12:58:39 AM\",\"sessionToken\":\"FQoDYXdzEIH//////////wEaDHKlf7uMLL744fS/RCLgAcSDdZYK7gVctXe76EuIIC+De68ZK21fz30fWwGuxRFmiMREIjLMZmxD/vMsNKLVoutHOLJzBs1VIi62uf8reZThmuU2eFQI1DVAM9Pmfr7iWySEX0ZzmaD9kuNPTM0T1OqudTqopDtgU0aRL0t6jlhASOK6UvH/2eNllSaFxU0l51GaUDfrKqRR9ejqAs0PyQx/0ymq71yqCRT2dVuyACVF9nbs0agt/y4Ke3T5MpKrjQUhPQF4c77sxGN3/OuMkx7G91pBYifjuOMx1SWf7PuqoU0hIEPmzmfmJdVMRbKpKK+CjNkF\"},\"assumedRoleUser\":{\"assumedRoleId\":\"AROAJMTKGPJI67TAWGXVG:vpc-flow-logging+279052847476\",\"arn\":\"arn:aws:sts::279052847476:assumed-role/flowlogsRole/vpc-flow-logging+279052847476\"}},\"requestID\":\"dc1636da-702e-11e8-a991-13cc235e6bd3\",\"eventID\":\"62c8bac9-c486-4e1e-9603-58d8ba4a20f4\",\"resources\":[{\"ARN\":\"arn:aws:iam::279052847476:role/flowlogsRole\",\"accountId\":\"279052847476\",\"type\":\"AWS::IAM::Role\"}],\"eventType\":\"AwsApiCall\",\"recipientAccountId\":\"279052847476\",\"sharedEventID\":\"c06bf41d-9758-4b33-abdb-86774f67c5c9\"}",
            "EventName": "AssumeRole",
            "EventSource": "sts.amazonaws.com",
            "Resources": [
                {
                    "ResourceType": "AWS::IAM::AccessKey",
                    "ResourceName": "ASIAIOD3JIGRTBSRNP7A"
                },
                {
                    "ResourceType": "AWS::STS::AssumedRole",
                    "ResourceName": "vpc-flow-logging+279052847476"
                },
                {
                    "ResourceType": "AWS::STS::AssumedRole",
                    "ResourceName": "arn:aws:sts::279052847476:assumed-role/flowlogsRole/vpc-flow-logging+279052847476"
                },
                {
                    "ResourceType": "AWS::STS::AssumedRole",
                    "ResourceName": "AROAJMTKGPJI67TAWGXVG:vpc-flow-logging+279052847476"
                },
}]

2 回复 | 直到 6 年前

fafl 6 年前

尝试以下条件:

if 'Username' in element:

leoschet 6 年前

使用 try-except 声明

try:
    username = element['Username']
except KeyError:
    # Deal with it
    username = None

# note that the try statement does not create a new scope
if username is not None:
    print(username)

您可以很容易地将此结构用于其他键。

为了完整起见,我应该注意到 else 和 finally 连同 尝试除外 . 这个 其他的 只有在 except 不是。 最后 不管发生什么都会跑的。