Pythonic way to determine if json object contains a certain value?

Question

I have a json object I get returned from a call, similar to this:

{
    'Tags': [
        {
            'Key': 'Dept',
            'PropagateAtLaunch': True,
            'ResourceId': 'my-auto-scaling-group',
            'ResourceType': 'auto-scaling-group',
            'Value': 'Research',
        },
        {
            'Key': 'Role',
            'PropagateAtLaunch': True,
            'ResourceId': 'my-auto-scaling-group',
            'ResourceType': 'auto-scaling-group',
            'Value': 'WebServer',
        },
        {
            'Key': 'ecs_scaling',
            'PropagateAtLaunch': True,
            'ResourceId': 'my-auto-scaling-group',
            'ResourceType': 'auto-scaling-group',
            'Value': 'true',
        },
    ],
    'ResponseMetadata': {
        '...': '...',
    },
}

Is there a more Pythonic way of simply determining whether or not the Key ecs_scaling exists, other than the standard:

data = json.loads(theThing)
for key in data.items():
   ... 

The Key could be the first item, it could be the 40th item -- ideally I'd like to be able to do something like if 'ecs_scaling' in theKeys: ... ?

Answer 1

You can use the builtin any.

Return True if any element of the iterable is true. If the iterable is empty, return False.

if any(tag['key'] == 'ecs_scaling' for tag in data['Tags']):
    ...

Answer 2

The complexity is already linear, so the only faster thing that you could hope for is a hash search. However, constructing a hash set or a hash table would require a linear complexity.

So unless the functions you call from the json module already build such a hash set, an iteration is the best thing you can do, for a linear complexity, ie O(n).

In this regard, I think the most Pythonic approach is using the any built-in, already mentioned by the other.

For the sake of completeness, although it would be less performant, you could go with a list comprehension as well, which is often considered as "highly Pythonic":

'ecs_scaling' in [item['Key'] for item in data.items()]

This is not as good, because an additional list has to be constructed, which requires an iteration over the whole data.

Answer 3

any(el['Key'] == 'ecs_scaling' for el in data['Tags'])