Using ExpressionAttributeNames to alias DynamoDB reserved keywords

dynamodb-update-reserved.py

from __future__ import print_function

import boto3
import json
import decimal

from boto3.dynamodb.conditions import Key, Attr
from botocore.exceptions import ClientError

from pprint import pprint
# Helper Class to convert a DDB Item to JSON

class DecimalEncoder(json.JSONEncoder):
	def default(self,o):
		if isinstance(o, decimal.Decimal):
			if o % 1 > 0:
				return float(o)
			else:
				return int(o)
		return super(DecimalEncoder, self).default(o)





dynamodb = boto3.resource('dynamodb', region_name='us-east-1')

table = dynamodb.Table('test-table')


# Adding movie:  2013 This Is the End

item_type = 'tenant'
id = 'test1oct25'

def test_get():
	try:
		response = table.get_item(
			Key = {
				'id': id,
				'item-type': item_type

			}

		)
	except ClientError as e:
		print(e.response['Error']['Message'])

	else:
		item = response['Item']
		print('GetItem succeeded:')
		print(json.dumps(item, indent=4, cls=DecimalEncoder))


def test_update():
	try:
		response = table.update_item(
			Key = {
				'id': id,
				'item-type': item_type

			},
			UpdateExpression="set #d.currency = :c",
			ExpressionAttributeValues = {
				':c': 'VND',
			},
			ExpressionAttributeNames = {
				'#d': 'data'
			},
			ReturnValues="UPDATED_NEW"

		)
	except ClientError as e:
		print(e.response['Error']['Message'])

	else:
		print('UpdateItem succeeded:')
		print(json.dumps(response, indent=4, cls=DecimalEncoder))	

test_update()