如何找到包含特定字符串和最大数字的对象？答案

【问题标题】：How to find an object which contains a specific string and a number which is the highest number?如何找到包含特定字符串和最大数字的对象？
【发布时间】：2018-05-20 08:28:24
【问题描述】：

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)

这是我运行命令得到的输出的一部分：

{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'}

好像输出已经按照最新的对象排序了。

我想解析包含单词“Dev”的堆栈的名称，并且在同一环境（Dev）的其余堆栈中编号最高的，在本例中为“Company-Dev-31 ”。

如何实现？

【问题讨论】：

在print 之前添加if 'dev' in st['StackName'].lower(): ?
谢谢！请创建一个答案。

标签： python amazon-cloudformation boto3

【解决方案1】：

要添加到 Martin 的答案，您可以从每个包含“Dev”的条目中获取数字，然后使用列表推导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)'}]

【讨论】：

【解决方案2】：

意大利，

首先使用名称中包含 Dev 的堆栈创建一个子列表，然后使用 Dev 编号作为键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“单线”。

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 中符合条件的那些元素

sorted 使用产生排序值的指定函数创建一个排序列表。

【讨论】：

【解决方案3】：

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)'}

将第一个转换为小写具有使测试大小写不敏感的效果，因此Dev 或dev 将匹配。

【讨论】：