How to get the value of a key in python dictionary

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?

There's nothing in the code fragment you posted that's even capable of producing any output, so it's not very clear what you're asking here. — jasonharper
– jasonharper, Commented Apr 22, 2020 at 9:32
Your code should actually raise a KeyError, so please edit your question with a PROPER minimal reproducible example and the full matching traceback. Also note that python has a very comprehe,sive tutorial, a full documentation, an interactive shell and a step debugger, so use all those features before posting here. — bruno desthuilliers
– bruno desthuilliers, Commented Apr 22, 2020 at 9:33

Devansh Soni · Accepted Answer · 2020-04-22 09:39:20Z

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.

George Shuklin · Accepted Answer · 2020-04-22 09:32:37Z

 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.

Sherk · Accepted Answer · 2020-04-22 09:38:31Z

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".

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