localstack to run for same code without adding endpoint_url - amazon-s3

Question

Let's say I have below code in boto3:
s3_client = boto3.client("s3")
def upload_file(file_name, bucket, object_name=None):
"""
Upload a file to a S3 bucket.
"""
try:
if object_name is None:
object_name = os.path.basename(file_name)
response = s3_client.upload_file(
file_name, bucket, object_name)
except ClientError:
logger.exception('Could not upload file to S3 bucket.')
raise
else:
return response
This works fine for actual AWS environment. Now I'm introducing localstack as testing framework prior doing the actual AWS upload.
My question is how to add localstack to this script with out changing the code.
I know if you add the endpoint_url to the boto3 client then it will work just for localstack.
But my question is there anyway I can use the same script for both localstack if localsystem is involved while for rest actual AWS will be used?

Answer 1

You can easily create a boto3 client that interacts with your LocalStack instance. Here is how you can modify your script for that purpose:
endpoint_url = "http://localhost.localstack.cloud:4566"
# alternatively, to use HTTPS endpoint on port 443:
# endpoint_url = "https://localhost.localstack.cloud"
s3_client = boto3.client("s3", endpoint_url=endpoint_url)
def upload_file(file_name, bucket, object_name=None):
"""
Upload a file to a S3 bucket.
"""
try:
if object_name is None:
object_name = os.path.basename(file_name)
response = s3_client.upload_file(
file_name, bucket, object_name)
except ClientError:
logger.exception('Could not upload file to S3 bucket.')
raise
else:
return response
Alternatively, if you prefer to (or need to) set the endpoints directly, you can use the $LOCALSTACK_HOSTNAME environment variable which is available when executing user code in LocalStack:
import os
endpoint_url = f"http://{os.getenv("LOCALSTACK_HOSTNAME")}:{os.getenv("EDGE_PORT")}"
client = boto3.client("s3", endpoint_url=endpoint_url)