get_base_python_image_uri() returns URIs for unsupported Python versions #6539

PySDK Version

• PySDK V2 (2.x)
• PySDK V3 (3.x)

Describe the bug
The get_base_python_image_uri() function returns image URIs for Python versions that don't have corresponding base images in ECR. When these URIs are used in SageMaker jobs, they fail with image not found errors.

To reproduce

from sagemaker.core.image_uris import get_base_python_image_uri

# Request Python 3.11 base image - THIS FAILS
uri_311 = get_base_python_image_uri(region="us-east-1", py_version="311")
print(f"Python 3.11 URI: {uri_311}")
# Attempt to use this URI in a SageMaker job will fail

# Request Python 3.10 base image - THIS WORKS
uri_310 = get_base_python_image_uri(region="us-east-1", py_version="310")
print(f"Python 3.10 URI: {uri_310}")
# Works fine with SageMaker jobs

Only Python 3.8 and 3.10 have corresponding base images in ECR. Attempting to use Python 3.11, 3.13, or any other unsupported version results in a failure when the SageMaker job tries to pull the image.

Expected behavior
The function should either:

1. Only accept Python versions for which base images actually exist in ECR (currently 3.8 and 3.10)
2. Raise a clear ValueError listing the supported Python versions
3. Update the docstring to document which Python versions are supported

Screenshots or logs

Error occurs only when using unsupported Python versions (e.g., 3.11):

botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the CreateTrainingJob operation: Cannot find the requested image: 012345678901.dkr.ecr.us-west-2.amazonaws.com/sagemaker-base-python-311:1.0 with tag: 1.0 and digest: null. Please check if your ECR image exists and role arn:aws:iam::123456789012:role/SM-Training-ABCDEFGHIJ has proper pull permissions for SageMaker: ecr:BatchCheckLayerAvailability, ecr:BatchGetImage, ecr:GetDownloadUrlForLayer

The issue is that the base image sagemaker-base-python-311 does not exist in ECR. Using Python 3.10 works without this error.

System information

• SageMaker Python SDK version: 3.x
• Framework name: N/A (base Python image issue)
• Framework version: N/A
• Python version: 3.11, 3.13 (attempted), 3.10 working
• CPU or GPU: N/A
• Custom Docker image: N/A

Additional context
The function's docstring states "Can be 310 or 38", but the function accepts any string value for py_version without validation. This creates a discrepancy between documented and actual supported versions, and affects automated image discovery.