如何使用对象列表从JSON响应中获取特定的键值，并从提取的值中执行算术操作

Question

我编写了从API获取数据的代码。我能够解析API中的JSON数据。我只通过API过滤出正在运行的实例并提取其数据。输出是一个JSON响应。

我想：

instances.

• and

1. 检索运行实例的corecount和ThreadsPerCore值，
2. 稍后将不得不将运行实例的所有vcpus相乘的corecountx ThreadsPerCore = vcpus相加。H 212G 213

我如何编写这样做的代码？

我读了一些教程，所以我知道我需要使用[]来访问嵌套列表和字典的元素；我尝试使用它来检索单个数据集(例如-1)的值，但是在我的例子中，我无法确切地知道它是如何工作的，我可能有'n‘个数据集(实例1，2，3，……)需要获得具有特定值的数据。因此，我在这里实现了for loop，当我不得不执行算术操作时，工作也变得复杂起来。

在本例中，JSON输出结构包含3组数据(针对3个正在运行的实例)，但根据场景可能有所不同：

{
    "Reservations": [
        {
            "Groups": [],
            "Instances": [
                {
                "AmiLaunchIndex": 0,
                "ImageId": "ami-123",
                "InstanceId": "INSTANCE-1",
                "InstanceType": "t2.micro",
                "KeyName": "MyKeyPair",
                "State": {
                    "Code": 16,
                    "Name": "running"
                },
                "StateTransitionReason": "",
                "CpuOptions": {
                    "CoreCount": 4,
                    "ThreadsPerCore": 2
                },
     ],
        "OwnerId": "123456789012"
        "ReservationId": "r-02a3f596d91211712",
    },
    {
            "Groups": [],
            "Instances": [
                {
                "AmiLaunchIndex": 0,
                "ImageId": "ami-123",
                "InstanceId": "INSATNCE-2",
                "InstanceType": "t2.micro",
                "KeyName": "MyKeyPair",
                "State": {
                    "Code": 16,
                    "Name": "running"
                },
                "StateTransitionReason": "",
                "CpuOptions": {
                    "CoreCount": 8,
                    "ThreadsPerCore": 2
                },
     ],
        "OwnerId": "123456789012"
        "ReservationId": "r-02a3f596d91211712",
    },
    {
            "Groups": [],
            "Instances": [
                {
                "AmiLaunchIndex": 0,
                "ImageId": "ami-123",
                "InstanceId": "INSTANCE-3",
                "InstanceType": "t2.micro",
                "KeyName": "MyKeyPair",
                "State": {
                    "Code": 16,
                    "Name": "running"
                },
                "StateTransitionReason": "",
                "CpuOptions": {
                    "CoreCount": 4,
                    "ThreadsPerCore": 2
                },
     ],
        "OwnerId": "123456789012"
        "ReservationId": "r-02a3f596d91211712",
    }
  ]
}

检索CpuOptions：CoreCount和ThreadsPerCore值的代码如下：

from shell import run_command_str
import json
cmd = "aws ec2 describe-instances  --output json --filters Name=instance-state-name,Values=running"
output = run_command_str(command=cmd, shell_command=True)
status = json.loads(output)

corecount = {}
for reservation in status1["Reservations"]:
    for instance in reservation["Instances"]:
        corecount[instance["InstanceId"]] = instance["CpuOptions"]["CoreCount"]
print(corecount)

threadspercore = {}

for reservation in status1["Reservations"]:
    for instance in reservation["Instances"]:
        threadspercore[instance["InstanceId"]] = instance["CpuOptions"]["ThreadsPerCore"]
print(threadspercore)

此代码的输出：

{'INSTANCE-1': 4, 'INSTANCE-2': 8, 'INSTANCE-3': 4}  ###corecount values
{'INSTANCE-1': 2, 'INSTANCE-2': 2, 'INSTANCE-3': 2}   ###Threadpercore values

Answer 1

如果我正确地理解了你，你想要计算vcpus和来自corecount和threadspercore的所有vcpus之和。

corecount = {"INSTANCE-1": 4, "INSTANCE-2": 8, "INSTANCE-3": 4}
threadspercore = {"INSTANCE-1": 2, "INSTANCE-2": 2, "INSTANCE-3": 2}

vcpus = {k: corecount[k] * threadspercore[k] for k in corecount}
sum_vcpus = sum(vcpus.values())

print(corecount)
print(threadspercore)
print(vcpus)
print(sum_vcpus)

指纹：

{'INSTANCE-1': 4, 'INSTANCE-2': 8, 'INSTANCE-3': 4}
{'INSTANCE-1': 2, 'INSTANCE-2': 2, 'INSTANCE-3': 2}
{'INSTANCE-1': 8, 'INSTANCE-2': 16, 'INSTANCE-3': 8}
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