如何使用itertools将返回的值从一个函数传递给另一个函数？

Question

我有一个列表被返回为

[('10.12.250.29', 'pdx02-he-trial-ansible01', 'us-west-2a', 'vol-e7775a10'), ('10.12.32.22', 'pdx02-cloud-prod-ansible01 Clone ', 'us-west-2b', 'vol-b0607d70'), ('10.12.0.20', 'pdx02-cloud-trial/dev-ansible01', 'us-west-2a', 'vol-b32e5c46'), ('10.12.250.7', 'pdx02-he-prod-ansible01', 'us-west-2a', 'vol-fd94400b'), ('10.12.250.4', 'pdx02-he-dev-ansible01', 'us-west-2a', 'vol-ee6abf18'), ('10.12.32.16', 'pdx02-cloud-prod-ansible', 'us-west-2b', 'vol-ae49adbb'), ('10.121.15.22', 'ansible-classic', 'us-west-2a', 'vol-f893c20d'), ('10.17.15.145', 'pdx01-ms-dev-ansible', 'us-west-2a', 'vol-e2d45515'), ('10.21.32.27', 'fra01-cloud-prod-ansible', 'eu-central-1b', 'vol-5f86f5bd'), ('10.21.250.13', 'fra01-he-trial-ansible01', 'eu-central-1a', 'vol-f9e7d220'), ('10.21.250.27', 'fra01-he-dev-ansible01', 'eu-central-1a', 'vol-f6e3fa2f'), ('10.21.0.9', 'fra01-cloud-dev-ansible01', 'eu-central-1a', 'vol-98104671'), ('10.21.250.5', 'fra01-he-prod-ansible01', 'eu-central-1a', 'vol-809b8259'), ('10.31.250.26', 'sin01-he-dev-ansible01', 'ap-southeast-1a', 'vol-86443940'), ('10.31.250.19', 'sin01-he-prod-ansible01', 'ap-southeast-1a', 'vol-bebcc178'), ('10.31.32.12', 'sin01-cloud-prod-ansible01', 'ap-southeast-1b', 'vol-01409de9'), ('10.31.250.27', 'sin01-he-trial-ansible01', 'ap-southeast-1a', 'vol-f6cdc631'), ('10.31.0.18', 'sin01-cloud-dev-ansible01', 'ap-southeast-1a', 'vol-3c0aac28')]

这基本上是：

<IP_ADDRESS> , <AWS_TAG_NAME> , <REGION> , <VOLUME>

现在，我将其传递给另一种方法，在该方法中，我需要提取每个值并将其单独存储，因此我使用了来自__main__ itertools ：

data = list(itertools.chain(*ansible_box_info))
print "-----------------"
print data
#mapping = {i[0]: [i[1], i[2]] for i in data}
print "Now Calling the Snapshot Creater!"
call_snapshot_creater(data)

def call_snapshot_creater(passed_data):
    ip_address = ','.join(list(itertools.chain(*[[j[0] for j in i] for i in data])))
    tags_descrip = list(itertools.chain(*[[j[1] for j in i] for i in data]))
    regions_az = list(itertools.chain(*[[j[2] for j in i] for i in data]))
    volume_id = list(itertools.chain(*[[j[3] for j in i] for i in data]))

这打破了上面的列表，只选择了所有内容的首字母，即ip_address打印：

1,p,u,v,1,p,u,v,1,p,u,v,1,p,u,v,1,p,u,v,1,p,u,v,1,a,u,v,1,p,u,v,1,f,e,v,1,f,e,v,1,f,e,v,1,f,e,v,1,f,e,v,1,s,a,v,1,s,a,v,1,s,a,v,1,s,a,v,1,s,a,v

代替10.12.250.29，10.12.32.22 ..................

如何使用迭代器正确打破这一点？

我试图通过将这些值传递给快照创建者来创建快照：

def call_snapshot_creater(passed_data):
    ip_address = ','.join(list(itertools.chain(*[[j[0] for j in i] for i in data])))
    tags_descrip = list(itertools.chain(*[[j[1] for j in i] for i in data]))
    regions_az = list(itertools.chain(*[[j[2] for j in i] for i in data]))
    volume_id = list(itertools.chain(*[[j[3] for j in i] for i in data]))

    regions = ['us-west-2', 'eu-central-1', 'ap-southeast-1']

    for region in regions:
        ec2 = boto3.resource('ec2', region, aws_access_key_id=ACCESS_KEY, aws_secret_access_key=SECRET_KEY, )
        print "Snapshot Creation For Ansible -> ",ip_address," initiated , tag = ", tags_descrip ,"region : ", regions_az
        print "Snapshot will be created with -> Name : ",tags_descrip
        snapshot = ec2.create_snapshot(VolumeId=volume_id, Description=tags_descrip)
        print snapshot.id
        print "Snapshot is being created for Ansible box ", tags_descrip ,"with snapshot id :",snapshot.id
        #slack.chat.post_message(slack_channel,"Creating Snapshot for The volume"+ str(snapshot.id),username='Ansible_box_snapshot_bot')
        snapshot.load()
        while snapshot.state != 'completed':
            print "The Snapshot :", snapshot.id , "for Ansible box named : ", tags_descrip  ,"is currently in :",snapshot.state," state"
            time.sleep(30)
            snapshot.load()
            print snapshot.progress
        else:
            print "Snapshot ",snapshot.id, "for Ansible box ", tags_descrip , "is now Ready!! Final state ->",snapshot.state

Answer 1

使用[[j[0] for j in i] for i in data]您将遍历该列表，并计算[j[0] for j in i] ，其中i是当前元组。 因此，您遍历元组，其中j是当前字符串，并获得该字符串的第一个字符。

但是，您想要的只是元组的第一项。 这意味着您甚至不需要itertools.chain ：使用[i[0] for i in data] 。 这将获取每个元组的第一个元素，并产生预期的输出。

因此，这是更改后的代码：

ip_address = ','.join(i[0] for i in data)  # you can use an iterator here
tags_descrip = ','.join(i[1] for i in data)
regions_az = ','.join(i[2] for i in data)
volume_id = ','.join(i[3] for i in data)

但是，这可以全部一行完成：

ip_address, tags_descrip, regions_az, volume_id = (','.join(j[i] for j in data) for i in range(4))

另一个可能性如下：（这里您仅对data一次迭代，但是可读性不强）

ip_address, tags_descrip, regions_az, volume_id = map(','.join, zip(*data))

这是第二个方法的工作原理（我认为第一个是不言而喻的）：

您将以下元组传递给zip ：

IP, ... from the first tuple
IP, ... from the second tuple
   .
   .
   .

因此，所有不同的字段都是对齐的。 zip为您提供了一个迭代器，该迭代器返回包含每个列表的第一项的元组，然后返回包含第二项的元组，依此类推。 因此，如果您要调用list(zip(*data)) ，则将具有一个用于输入的列表：所有IP，依此类推。

我会选择第一个选项而不是第二个选项，因为第一个选项更具可读性，但是如果您确实关心性能（我想在这种情况下您不会使用Python），那么第二个选项是要走的路。

我希望我能帮上忙，

代号Lambda

Answer 2

您没有使用chain并正确拆箱 。 您尝试做的所有事情都可以通过zip 和解 zip viz完成。 zip(*...) ：

>>> l = [('10.12.250.29', 'pdx02-he-trial-ansible01', 'us-west-2a', 'vol-e7775a10'), ('10.12.32.22', 'pdx02-cloud-prod-ansible01 Clone ', 'us-west-2b', 'vol-b0607d70'), ('10.12.0.20', 'pdx02-cloud-trial/dev-ansible01', 'us-west-2a', 'vol-b32e5c46'), ('10.12.250.7', 'pdx02-he-prod-ansible01', 'us-west-2a', 'vol-fd94400b'), ('10.12.250.4', 'pdx02-he-dev-ansible01', 'us-west-2a', 'vol-ee6abf18'), ('10.12.32.16', 'pdx02-cloud-prod-ansible', 'us-west-2b', 'vol-ae49adbb'), ('10.121.15.22', 'ansible-classic', 'us-west-2a', 'vol-f893c20d'), ('10.17.15.145', 'pdx01-ms-dev-ansible', 'us-west-2a', 'vol-e2d45515')]
>>>
>>> data = zip(*l)
>>>
>>> ip_address = ','.join(next(data))
>>> ip_address
'10.12.250.29,10.12.32.22,10.12.0.20,10.12.250.7,10.12.250.4,10.12.32.16,10.121.15.22,10.17.15.145'
>>>
>>> tags_descrip = ','.join(next(data))
>>> tags_descrip
'pdx02-he-trial-ansible01,pdx02-cloud-prod-ansible01 Clone ,pdx02-cloud-trial/dev-ansible01,pdx02-he-prod-ansible01,pdx02-he-dev-ansible01,pdx02-cloud-prod-ansible,ansible-classic,pdx01-ms-dev-ansible'
>>>
>>> regions_az = ','.join(next(data))
>>> regions_az
'us-west-2a,us-west-2b,us-west-2a,us-west-2a,us-west-2a,us-west-2b,us-west-2a,us-west-2a'
>>>
>>> volume_id = ','.join(next(data))
>>> volume_id
'vol-e7775a10,vol-b0607d70,vol-b32e5c46,vol-fd94400b,vol-ee6abf18,vol-ae49adbb,vol-f893c20d,vol-e2d45515'