如何捕捉`botocore.errorfactory.UserNotFoundException`？

Question

我正在使用AWS Cognito 制作OAuth 服务器。我现在正在创建异常处理程序以防万一使用不存在，但 requests 打算得到一个

ipdb> pk
'David'
ipdb> res = self.cognito_client.admin_get_user(
            UserPoolId=settings.AWS_USER_POOL_ID,
            Username=pk
        )
*** botocore.errorfactory.UserNotFoundException: An error occurred (UserNotFoundException) when calling the AdminGetUser operation: User does not exist.
Traceback (most recent call last):
  File "/Users/sarit/.pyenv/versions/futuready-titan/lib/python3.8/site-packages/botocore/client.py", line 316, in _api_call
    return self._make_api_call(operation_name, kwargs)
  File "/Users/sarit/.pyenv/versions/futuready-titan/lib/python3.8/site-packages/botocore/client.py", line 626, in _make_api_call
    raise error_class(parsed_response, operation_name)

boto3==1.12.15            # via -r el.in
botocore==1.15.15         # via boto3, s3transfer
django==3.0.3
python3.8.1

我已经与botocore source codeUserNotFoundException核实过

问题：
我怎么能具体catch这个exception？

Answer 1

当botocore.error_factory创建异常时，不能直接导入。您应该使用生成的类来处理异常，而不是直接导入。

文档中为每个操作提供了可能的异常列表。例如，对于CognitoIdentityProvider.Client.admin_get_user，可能的例外是：

CognitoIdentityProvider.Client.exceptions.ResourceNotFoundException
CognitoIdentityProvider.Client.exceptions.InvalidParameterException
CognitoIdentityProvider.Client.exceptions.TooManyRequestsException
CognitoIdentityProvider.Client.exceptions.NotAuthorizedException
CognitoIdentityProvider.Client.exceptions.UserNotFoundException
CognitoIdentityProvider.Client.exceptions.InternalErrorException

有一个示例说明如何获取客户端的示例列表以及如何处理它（当然异常列表取决于操作）：

import boto3

eks = boto3.client('eks')
print(dir(eks.exceptions))
# ['BadRequestException', 
# 'ClientError', 
# 'ClientException',
# 'InvalidParameterException',
# 'InvalidRequestException',
# 'NotFoundException',
# 'ResourceInUseException',
# 'ResourceLimitExceededException',
# 'ResourceNotFoundException',
# 'ServerException',
# 'ServiceUnavailableException',
# 'UnsupportedAvailabilityZoneException', ...]
try:
    response = eks.list_nodegroups(clusterName='my-cluster')
except eks.exceptions.ResourceNotFoundException as e:
    # do something with e
    print("handled: " + str(e))

cognito_idp = boto3.client('cognito-idp')
print(dir(cognito_idp.exceptions))
# [ 'ClientError', 
# 'ConcurrentModificationException',
# 'DeveloperUserAlreadyRegisteredException',
# 'ExternalServiceException',
# 'InternalErrorException',
# 'InvalidIdentityPoolConfigurationException',
# 'InvalidParameterException',
# 'LimitExceededException',
# 'NotAuthorizedException',
# 'ResourceConflictException',
# 'ResourceNotFoundException',
# 'TooManyRequestsException', ... ]
try:
    response = cognito_idp.admin_get_user(
        UserPoolId='pool_id',
        Username='username'
    )
except cognito_idp.exceptions.UserNotFoundException as e:
    # do something with e
    print("handled: " + str(e))

此外，您可能会看到输入较少的 botocore.exceptions.ClientError 而不是特定的：

import boto3
import botocore.exceptions

try:
    response = cognito_idp.admin_get_user(
        UserPoolId='pool_id',
        Username='username'
    )
except botocore.exceptions.ClientError as e:
    # do something with e
    print("handled: " + str(e))

Answer 2

有两种方法，如果异常暴露在客户端，您可以直接捕获它，或者从 botocore.exceptions 导入并使用它。

选项 1：

try: 
    res = self.cognito_client.admin_get_user(
              UserPoolId=settings.AWS_USER_POOL_ID,
              Username=pk
          )
except self.cognito_client.exceptions.UserNotFoundException as e:
    print(e)

选项 2：

from botocore.exceptions import UserNotFoundException

try: 
    res = self.cognito_client.admin_get_user(
              UserPoolId=settings.AWS_USER_POOL_ID,
              Username=pk
          )
except UserNotFoundException as e:
    print(e)

有关更多详细信息，请参阅 boto 错误处理documentation。

Answer 3

这当然不是理想的，但我能够抓住它：

from botocore.exceptions import ClientError

try:
    func_that_interacts_with_cognito()
except ClientError:
    # This happens when the user is not found.
    print("It happened again ...")