For循环只获取lis中的最后一个元素

Question

我很抱歉问了一个简单的问题，但尝试了多个选项却没有任何解决方案。 我的问题是for循环只取列表（区域）中的最后一个值。你知道吗

import boto3
import csv
import io
from io import BytesIO
from email.mime.text import MIMEText
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart


ses = boto3.client('ses')
email_from = 'example@gmail.com'
email_to = 'example@gmail.com'
email_cc = 'example@gmail.com'
emaiL_subject = 'Unused_Security'
email_body = '***Link to S3 Object***'


def lambda_handler(event, context):
    regions = ['eu-west-1','eu-west-2','us-east-2','us-west-1','us-west-2','us-east-1']
    for region in regions:
        csvio = io.BytesIO()
        writer = csv.writer(csvio)
        writer.writerow([
            'Account Name',
            'Region',
            'Id'
        ])
        ec2 = boto3.resource('ec2', region_name=region)
        sgs = list(ec2.security_groups.all())
        insts = list(ec2.instances.all())
        all_sgs = set([sg.group_id for sg in sgs])
        all_inst_sgs = set([sg['GroupId'] for inst in insts for sg in
        inst.security_groups])
        unused_sgs = all_sgs - all_inst_sgs
        for elem in unused_sgs:
            writer.writerow([
                Account_Name,
                region,
                elem
                ])
        s3 = boto3.client('s3')
        s3.put_object(Body=csvio.getvalue(), ContentType='application/vnd.ms-excel', Bucket='unused-sg', Key='Unused_Security.csv', ACL='public-read') 

        csvio.close()
        s3.get_object(Bucket='unused-sg', Key='Unused_Security.csv') 
    response = ses.send_email(
        Source = email_from,
        Destination={
            'ToAddresses': [
                email_to,
            ],
            'CcAddresses': [
                email_cc,
            ]
        },
        Message={
            'Subject': {
                'Data': emaiL_subject
            },
            'Body': {
                'Text': {
                    'Data': email_body
                }
            }
        }
    )

这是一个列表，它只接受最后一个值

regions = ['eu-west-1','eu-west-2','us-east-2','us-west-1','us-west-2','us-east-1']

它必须获取列表（区域）中的所有值并显示结果。但它只需要最后一个值（us-east-1）。请告知是什么导致了错误。你知道吗

Answer 1

这一行中的每个循环都将覆盖csv文件s3.put_object(Body=csvio.getvalue(), ContentType='application/vnd.ms-excel', Bucket='unused-sg', Key='Unused_Security.csv', ACL='public-read')。 将它放在for循环之外，这样就只能在循环完成后才写入s3

Answer 2

此处：

for region in regions:
    csvio = io.BytesIO()
    writer = csv.writer(csvio)
    # ...
    s3.put_object(Body=csvio.getvalue(), ContentType='application/vnd.ms-excel', Bucket='unused-sg', Key='Unused_Security.csv', ACL='public-read') 

您正在为每个区域创建一个新的csv文件，覆盖上一个区域。你想不让这件事发生：

csvio = io.BytesIO()
writer = csv.writer(csvio)
for region in regions:
    # massage the data 
    # write to the csv
    # ...

# now we're outside the loop we write the full thing
s3 = boto3.client('s3')
s3.put_object(Body=csvio.getvalue(), ContentType='application/vnd.ms-excel', Bucket='unused-sg', Key='Unused_Security.csv', ACL='public-read') 
csvio.close()