How can I easily determine if a Boto 3 S3 bucket resource exists?

At the time of this writing there is no high-level way to quickly check whether a bucket exists and you have access to it, but you can make a low-level call to the HeadBucket operation. This is the most inexpensive way to do this check:

from botocore.client import ClientError

try:
    s3.meta.client.head_bucket(Bucket=bucket.name)
except ClientError:
    # The bucket does not exist or you have no access.

Alternatively, you can also call create_bucket repeatedly. The operation is idempotent, so it will either create or just return the existing bucket, which is useful if you are checking existence to know whether you should create the bucket:

bucket = s3.create_bucket(Bucket='my-bucket-name')

As always, be sure to check out the official documentation.

Note: Before the 0.0.7 release, meta was a Python dictionary.

As mentioned by @Daniel, the best way as suggested by Boto3 docs is to use head_bucket()

head_bucket() - This operation is useful to determine if a bucket exists and you have permission to access it.

If you have a small number of buckets, you can use the following:

>>> import boto3
>>> s3 = boto3.resource('s3')
>>> s3.Bucket('Hello') in s3.buckets.all()
False
>>> s3.Bucket('some-docs') in s3.buckets.all()
True
>>>