# Purchasing Reserved Instances (AWS SDKs)


The AWS SDKs (except the Android and iOS SDKs) support all the operations that are defined in the [Amazon OpenSearch Service API Reference](https://docs.aws.amazon.com/opensearch-service/latest/APIReference/Welcome.html), including the following:
+ `DescribeReservedInstanceOfferings`
+ `PurchaseReservedInstanceOffering`
+ `DescribeReservedInstances`

This sample script uses the [OpenSearchService](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/opensearch.html) low-level Python client from the AWS SDK for Python (Boto3) to purchase Reserved Instances. You must provide a value for `instance_type`.

```
import boto3
from botocore.config import Config

# Build the client using the default credential configuration.
# You can use the CLI and run 'aws configure' to set access key, secret
# key, and default region.

my_config = Config(
    # Optionally lets you specify a region other than your default.
    region_name='us-east-1'
)

client = boto3.client('opensearch', config=my_config)

instance_type = '' # e.g. m4.2xlarge.search


def describe_RI_offerings(client):
    """Gets the Reserved Instance offerings for this account"""

    response = client.describe_reserved_instance_offerings()
    offerings = (response['ReservedInstanceOfferings'])
    return offerings


def check_instance(offering):
    """Returns True if instance type is the one you specified above"""

    if offering['InstanceType'] == instance_type:
        return True

    return False


def get_instance_id():
    """Iterates through the available offerings to find the ID of the one you specified"""

    instance_type_iterator = filter(
        check_instance, describe_RI_offerings(client))
    offering = list(instance_type_iterator)
    id = offering[0]['ReservedInstanceOfferingId']
    return id


def purchase_RI_offering(client):
    """Purchase Reserved Instances"""

    response = client.purchase_reserved_instance_offering(
        ReservedInstanceOfferingId = get_instance_id(),
        ReservationName = 'my-reservation',
        InstanceCount = 1
    )
    print('Purchased reserved instance offering of type ' + instance_type)
    print(response)


def main():
    """Purchase Reserved Instances"""
    purchase_RI_offering(client)
```

For more information about installing and using the AWS SDKs, see [AWS Software Development Kits](https://aws.amazon.com/code).