I’m trying to write “good” python and capture a S3 no such key error with this:

session = botocore.session.get_session()
client = session.create_client('s3')
try:
    client.get_object(Bucket=BUCKET, Key=FILE)
except NoSuchKey as e:
    print >> sys.stderr, "no such key in bucket"

But NoSuchKey isn’t defined and I can’t trace it to the import I need to have it defined.

e.__class__ is botocore.errorfactory.NoSuchKey but from botocore.errorfactory import NoSuchKey gives an error and from botocore.errorfactory import * doesn’t work either and I don’t want to capture a generic error.

from botocore.exceptions import ClientError

try:
    response = self.client.get_object(Bucket=bucket, Key=key)
    return json.loads(response["Body"].read())
except ClientError as ex:
    if ex.response['Error']['Code'] == 'NoSuchKey':
        logger.info('No object found - returning empty')
        return dict()
    else:
        raise

Using botocore 1.5, it looks like the client handle exposes the exception classes:

session = botocore.session.get_session()
client = session.create_client('s3')
try:
    client.get_object(Bucket=BUCKET, Key=FILE)
except client.exceptions.NoSuchKey as e:
    print >> sys.stderr, "no such key in bucket"

In boto3, I was able to access the exception in resource’s meta client.

import boto3

s3 = boto3.resource('s3')
s3_object = s3.Object(bucket_name, key)

try:
    content = s3_object.get()['Body'].read().decode('utf-8')
except s3.meta.client.exceptions.NoSuchKey:
    print("no such key in bucket")

I think the most elegant way to do this is in Boto3 is

session = botocore.session.get_session()
client = session.create_client('s3')

try:
    client.get_object(Bucket=BUCKET, Key=FILE)
except client.exceptions.NoSuchKey:
    print("no such key in bucket")

The documentation on error handling seems sparse, but the following prints the error codes this works for:

session = botocore.session.get_session()
client = session.create_client('s3')
try:
    try:
        client.get_object(Bucket=BUCKET, Key=FILE)
    except client.exceptions.InvalidBucketName:
        print("no such key in bucket")
except AttributeError as err:
    print(err)

< botocore.errorfactory.S3Exceptions object at 0x105e08c50 > object has no attribute ‘InvalidBucketName’. Valid exceptions are: BucketAlreadyExists, BucketAlreadyOwnedByYou, NoSuchBucket, NoSuchKey, NoSuchUpload, ObjectAlreadyInActiveTierError, ObjectNotInActiveTierError