What is the fastest way to empty s3 bucket using boto3?

Based on previous responses, and adding check of versioning enabled, you can empty a bucket, with versions enabled or not doing:

s3 = boto3.resource('s3')
s3_bucket = s3.Bucket(bucket_name)
bucket_versioning = s3.BucketVersioning(bucket_name)
if bucket_versioning.status == 'Enabled':
    s3_bucket.object_versions.delete()
else:
    s3_bucket.objects.all().delete()

Just use aws cli.

aws s3 rm s3://mybucket --recursive

Well, for longer answer if you insists to use boto3. This will send a delete marker to s3. No folder handling required. bucket.Object.all will create a iterator that not limit to 1K .

import boto3    
s3 = boto3.resource('s3')
bucket = s3.Bucket('my-bucket')
# suggested by Jordon Philips 
bucket.objects.all().delete()

If versioning is enabled, there's a similar call to the other answer to delete all object versions:

import boto3
s3 = boto3.resource('s3')
bucket = s3.Bucket('bucket-name')
bucket.object_versions.delete()