How to handle errors with boto3?

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Use the response contained within the exception. Here is an example:

import boto3
from botocore.exceptions import ClientError

try:
    iam = boto3.client('iam')
    user = iam.create_user(UserName="fred")
    print("Created user: %s" % user)
except ClientError as e:
    if e.response['Error']['Code'] == 'EntityAlreadyExists':
        print("User already exists")
    else:
        print("Unexpected error: %s" % e)

The response dict in the exception will contain the following:

  • ['Error']['Code'] e.g. ‘EntityAlreadyExists’ or ‘ValidationError’
  • ['ResponseMetadata']['HTTPStatusCode'] e.g. 400
  • ['ResponseMetadata']['RequestId'] e.g. ‘d2b06652-88d7-11e5-99d0-812348583a35’
  • ['Error']['Message'] e.g. “An error occurred (EntityAlreadyExists) …”
  • ['Error']['Type'] e.g. ‘Sender’

For more information see:

[Updated: 2018-03-07]

The AWS Python SDK has begun to expose service exceptions on clients (though not on resources) that you can explicitly catch, so it is now possible to write that code like this:

import botocore
import boto3

try:
    iam = boto3.client('iam')
    user = iam.create_user(UserName="fred")
    print("Created user: %s" % user)
except iam.exceptions.EntityAlreadyExistsException:
    print("User already exists")
except botocore.exceptions.ParamValidationError as e:
    print("Parameter validation error: %s" % e)
except botocore.exceptions.ClientError as e:
    print("Unexpected error: %s" % e)

Unfortunately, there is currently no documentation for these errors/exceptions but you can get a list of the core errors as follows:

import botocore
import boto3
[e for e in dir(botocore.exceptions) if e.endswith('Error')]

Note that you must import both botocore and boto3. If you only import botocore then you will find that botocore has no attribute named exceptions. This is because the exceptions are dynamically populated into botocore by boto3.

You can get a list of service-specific exceptions as follows (replace iam with the relevant service as needed):

import boto3
iam = boto3.client('iam')
[e for e in dir(iam.exceptions) if e.endswith('Exception')]

[Updated: 2021-09-07]

In addition to the aforementioned client exception method, there is also a third-party helper package named aws-error-utils.

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