s3 head_object returns ClientError 404 instead of NoSuchKey error

What issue did you see ?

When the key does not exist in s3, s3 head_object returns a ClientError 404 instead of NoSuchKey error, making it harder to catch. Also, the doc says it should throw a NoSuchKey error. But get_object returns NoSuchKey.

Steps to reproduce

client.head_object(
    Bucket=bucket,
    Key=key,
)  # throws ClientError with code 404

client.get_object(
    Bucket=bucket,
    Key=key,
)  # throws NoSuchKey

Is this expected? If so, should the docs be modified? Thanks.

[adonig]

As a temporary workaround (implying the bug will get fixed one day) you can catch the ClientError like this:

import botocore
import boto3

s3_client = boto3.client("s3")
try:
    response = s3_client.head_object(Bucket="mybucket", Key="mykey")
except s3_client.exceptions.NoSuchKey:  # type: ignore
    pass   # TODO: Handle the exception here.
except botocore.exceptions.ClientError as err:
    # NOTE: This case is required because of https://github.com/boto/boto3/issues/2442
    if err.response["Error"]["Code"] == "404":
        pass  # TODO: Handle the exception here again.

That way your code will still work as expected in case the bug gets fixed.

[tim-finnigan]

Checking in - I believe the docs have been updated since this original issue was opened. In the head_object and get_object boto3 docs it now says:

• If you have the s3:ListBucket permission on the bucket, Amazon S3 returns an HTTP status code 404 (“no such key”) error.
• If you don’t have the s3:ListBucket permission, Amazon S3 returns an HTTP status code 403 (“access denied”) error.

If that still doesn’t clarify the behavior then any further requests for improvements to the documentation should be redirected to the S3 team because they own their API documentation as mentioned here earlier.

There is a Provide feedback link at the bottom of every API page where you can send direct feedback to the appropriate team. Alternatively you can reach out through AWS Support or we can forward requests internally. Please let us know if you had any follow up questions on this.