如何找到包含特定字符串和最大数字的对象？

Question

我是 Python 的初学者，我正在尝试使用 boto (CloudFormation) 列出最新创建的包含字符串的堆栈。

import boto3
client = boto3.client('cloudformation')
stacks = client.list_stacks(
    StackStatusFilter=[
        'CREATE_COMPLETE'
    ]
)

for st in stacks["StackSummaries"]:
    print(st)

这是我从运行命令获得的输出的一部分：

{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Dev-31/4d501360-d521-11e7-9aff-50a68a0bca9a', u'StackName': 'Company-Dev-31', u'CreationTime': datetime.datetime(2017, 11, 29, 16, 21, 6, 636000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Dev-30/4d501360-c231-11e7-8aca-50a68a0bca9a', u'StackName': 'Company-Dev-30', u'CreationTime': datetime.datetime(2017, 11, 29, 16, 21, 6, 644000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Stg-22/bc2b6c10-d41a-11e7-b1ab-50d5ca789eae', u'StackName': 'Company-Stg-22', u'CreationTime': datetime.datetime(2017, 11, 28, 9, 1, 34, 985000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Prod-US-API-64/0e85cc00-9602-11e7-8c08-50d5ca0184d2', u'StackName': 'Company-Prod-US-API-64', u'CreationTime': datetime.datetime(2017, 9, 10, 8, 28, 43, 598000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Prod-US-API-63/1ba257c0-9600-11e7-821f-503f20f2ad4a', u'StackName': 'Company-Prod-US-API-63', u'CreationTime': datetime.datetime(2017, 9, 10, 8, 14, 46, 602000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Prod-US-API-61/9252a9d0-2ace-11e7-8eea-503ac9ec2461', u'StackName': 'Company-Prod-US-API-61', u'CreationTime': datetime.datetime(2017, 4, 26, 22, 20, 36, 473000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Prod-US-API-60/1ba83440-2acd-11e7-a0c3-503a90a9c435', u'StackName': 'Company-Prod-US-API-60', u'CreationTime': datetime.datetime(2017, 4, 26, 22, 10, 7, 890000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines'}

似乎输出已经按照最新的对象排在第一位。

我想解析包含单词 "Dev" 的堆栈的名称，并且在相同环境 (Dev) 的其余堆栈中数字最高，在本例中为 "Company-Dev-31".

如何实现？

Answer 1

您可以使用 in 测试是否存在某些字符，如下所示：

import boto3
client = boto3.client('cloudformation')
stacks = client.list_stacks(
    StackStatusFilter=[
        'CREATE_COMPLETE'
    ]
)

for st in stacks["StackSummaries"]:
    if 'dev' in st['StackName'].lower():
        print(st)

这会给你：

{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Dev-31/4d501360-d521-11e7-9aff-50a68a0bca9a', u'StackName': 'Company-Dev-31', u'CreationTime': datetime.datetime(2017, 11, 29, 16, 21, 6, 636000), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}
{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Dev-30/4d501360-c231-11e7-8aca-50a68a0bca9a', u'StackName': 'Company-Dev-30', u'CreationTime': datetime.datetime(2017, 11, 29, 16, 21, 6, 644000), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}

首先转换为小写具有使测试用例不敏感的效果，因此 Dev 或 dev 将匹配。

Answer 2

板材，

首先用名称中包含 Dev 的那些堆栈创建一个子列表，然后使用 Dev 编号作为关键字对结果列表进行排序。

# make a list of stacks with Dev in stack ID
sublist = [ s for s in stacks if 'Dev' in s['StackId'] ]

# Extract a number from stack ID
REGEX = re.compile("Dev-([0-9]+)")
def extractNum(stack):
    match = REGEX.search(stack['StackId'])
    if match:
        return int(match.group(1))
    else:
        return None

# Sort the stack list in descending order
sublist.sort(key=extractNum, reverse=True)
print(sublist[0])

如果您愿意，可以使用内置函数和 lambda 将其压缩为 'one liner'。

REGEX = re.compile("Dev-([0-9]+)")
sublist = sorted(filter(lambda s: 'Dev' in s['StackId'], 
                        stacks),
    key = lambda s: int(REGEX.search(s['StackId']).group(1)),
    reverse = True
    );

filter 生成一个迭代器，它只包含 stacks 中满足条件

的那些元素

sorted 使用生成排序值的指定函数生成排序列表。

Answer 3

要添加到 Martin 的答案中，您可以从包含 'Dev' 的每个条目中获取数字，然后使用列表理解来检索具有最高数字的条目：

numlist = []

for item in st:
    if 'Dev' in item['StackName']:
        num = int(item['StackName'].split('Dev-')[1])
        numlist.append(num)

result = [i for i in st if ('Dev-%s' % max(numlist)) in i['StackName']]

print(result)

给予：

[{u'StackId': 'arn:aws:cloudformation:us-west-2:AWSACCOUNTID:stack/Company-Dev-31/4d501360-d521-11e7-9aff-50a68a0bca9a', u'StackName': 'Company-Dev-31', u'CreationTime': datetime.datetime(2017, 11, 29, 16, 21, 6, 636000, tzinfo=tzutc()), u'StackStatus': 'CREATE_COMPLETE', u'TemplateDescription': 'Company - Formation of Server Machines @ Oregon (us-west-2)'}]

如何找到包含特定字符串和最大数字的对象？

How to find an object which contains a specific string and a number which is the highest number?

python

amazon-cloudformation

boto3