aws-sdk-python-usage

Files (9)

• LICENSE
• SKILL.md
• configuration.md · references/
• credentials.md · references/
• dynamodb.md · references/
• error-handling.md · references/
• pagination.md · references/
• s3.md · references/
• waiters.md · references/

SKILL.md (first lines)

> Do not use emojis in any code, comments, or output when this skill is active.

# AWS SDK for Python (boto3)

boto3 is the high-level Python SDK for AWS. It wraps botocore (the low-level
SDK) and provides two distinct interfaces: **clients** (low-level, 1:1 API
mapping) and **resources** (high-level, object-oriented). Understanding which to
use and when is essential.

## Client vs Resource

**Clients** map directly to AWS service APIs. Every service has a client.
Responses are plain dicts.

**Resources** provide an object-oriented interface with attributes and actions.
Only some services have resources (S3, DynamoDB, EC2, IAM, SQS, SNS,
CloudFormation, CloudWatch, Glacier). Resources auto-marshal types (especially
useful for DynamoDB).

```python
import boto3

# Client - low-level, all services
s3_client = boto3.client("s3")
response = s3_client.list_buckets()
buckets = response["Buckets"]  # plain dicts

# Resource - high-level, select services
s3_resource = boto3.resource("s3")
for bucket in s3_resource.buckets.all():
    print(bucket.name)  # attribute access, not dict keys
```

Use clients when you need full API coverage or the service has no resource
interface. Use resources when they exist and simplify your code (especially
DynamoDB and S3).

## Session and Client Creation

```python
import boto3

# Default session implicitly created
client = boto3.client("s3")
resource = boto3.resource("dynamodb")

# Explicit session use when you need to customize how
# clients are created, use an explicit profile, etc.
session = boto3.Session(
    profile_name="my-profile",
    region_name="us-west-2",
)
client = session.client("s3")
```

Do not create clients inside loops - reuse a single client instance.  Clients
are thread safe and can be shared across threads once they're instantiated.

## Making API Calls

```python
# Client - pass parameters as keyword arguments, get dicts back
response = client.get_object(Bucket="my-bucket", Key="my-key")
data = response["Body"].read()

# Resource - use object methods and attributes
obj = s3_resource.Object("my-bucket", "my-key")
response = obj.get()
data = response["Body"].read()
```

Parameter names match the exact casing of the AWS API,
which is typically PascalCase, not snake\_case.

## Error Handling

Only catch exceptions when you have something actionable to do - return a
fallback value, retry, take a different code path. Catching an exception just to
print it and swallow it is wrong: it hides the real error and prevents callers
from reacting. Let exceptions propagate by default.

When you do catch, prefer typed exceptions on the client over generic
`ClientError` with string code matching through the `client.exceptions`
attribute:

```python
lambda_client = boto3.client("lambda")

def get_function_config(name: str) -> dict | None:
    """Return function configuration, or None if it doesn't exist."""
    try:
        return lambda_client.get_function_configuration(FunctionName=name)
    except lambda_client.exceptions.ResourceNotFoundException:
        return None  # actionable: convert missing function to None
    # Everything else propagates - caller or main() handles it
```

Use generic `ClientError` only as a catch-all in a top-level error handler, not
in business logic functions. It lives in botocore, not boto3:

```python
from botocore.exceptions import ClientError

def main() -> int:
    try:
        result = do_the_work()
        print(result)
        return 0
    except ClientError as e:
        print(f"Error: {e}", file=sys.stderr)
        return 1
```

For the full error hierarchy and botocore exceptions, see `references/error-handling.md`.

## Script Structure

When asked to write a script that uses `boto3` or `botocore`, keep `if __name__
== "__main__"` to a single function call. Argument parsing, error presentation,

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