如何获取 python 字典中键的值

Question

I have this python output that retrieves a dictionary like below. I want to get the value of TopicArn that falls inside NotificationConfiguration .

This is my output looks like.

output of clusters

{
    'Marker': 'string',
    'CacheClusters': [
        {
            'CacheClusterId': 'string',
            'ConfigurationEndpoint': {
                'Address': 'string',
                'Port': 123
            },
            'ClientDownloadLandingPage': 'string',,
            'PendingModifiedValues': {
                'NumCacheNodes': 123,
                'CacheNodeIdsToRemove': [
                    'string',
                ],
                'EngineVersion': 'string',
                'CacheNodeType': 'string',
                'AuthTokenStatus': 'SETTING'|'ROTATING'
            },
            'NotificationConfiguration': {
                'TopicArn': 'string',
                'TopicStatus': 'string'
            },        
            'ReplicationGroupId': 'string',
        },
    ]
}

This is what I tried:

def get_ec_cache_Arn(region, clusters):
    ec_client = boto3.client('elasticache', region_name=region)

    count = 1

    for cluster in clusters['CacheClusters']:
        cluster_arn = cluster['NotificationConfiguration'][0]['TopicArn']

But this doesn't work. gives no output. But clusters has a value I am passing from some other function. When I print clusters it produces the above-mentiond dictionary. That means clusters is not empty.

Can someone help me?

Answer 1

Modify your for loop. You've put [0] there which will throw KeyError because in python dictionaries are not ordered and you can't use indexing with them.

for cluster in clusters['CacheClusters']:
        cluster_arn = cluster['NotificationConfiguration']['TopicArn']

This gives desired output.

Answer 2

   for cluster in clusters['CacheClusters']:
        cluster_arn = cluster['NotificationConfiguration']['TopicArn']

You have an excessive [0] in your code. You've tried to acces element 0 , but 'NotificationConfiguration' is a dictionary and not a list.

Answer 3

I'd like to share a general method to access dictionary elements:

for key, value in clusters.items():
  assert clusters[key] == value, "access the value according to the key".