Python(boto3)에서의 DynamoDB TransactWriteItems

import boto3

client = boto3.client("dynamodb")

# Move one award between two songs — atomically. If the first song has no
# award to give, NEITHER update happens.
try:
    client.transact_write_items(
        TransactItems=[
            {
                "Update": {
                    "TableName": "Music",
                    "Key": {"Artist": {"S": "Arturo Sandoval"}, "SongTitle": {"S": "Cubano Chant"}},
                    "UpdateExpression": "SET #upd0 = #upd0 - :one",
                    "ConditionExpression": "#upd0 >= :one",
                    "ExpressionAttributeNames": {"#upd0": "Awards"},
                    "ExpressionAttributeValues": {":one": {"N": "1"}},
                }
            },
            {
                "Update": {
                    "TableName": "Music",
                    "Key": {"Artist": {"S": "Arturo Sandoval"}, "SongTitle": {"S": "A Mis Abuelos"}},
                    "UpdateExpression": "SET #upd0 = if_not_exists(#upd0, :zero) + :one",
                    "ExpressionAttributeNames": {"#upd0": "Awards"},
                    "ExpressionAttributeValues": {":one": {"N": "1"}, ":zero": {"N": "0"}},
                }
            },
        ]
    )
    print("Transaction committed")
except client.exceptions.TransactionCanceledException as e:
    # One reason per action, in TransactItems order. Code "None" means that
    # action was fine — some OTHER action sank the transaction.
    codes = [reason["Code"] for reason in e.response["CancellationReasons"]]
    print(f"Transaction canceled: {codes}")  # e.g. ['ConditionalCheckFailed', 'None']