How to check if DynamoDB table exists?

I'm a new user in boto3 and i'm using DynamoDB.

I went through over the DynamoDB api and I couldn't find any method which tell me if a table is already exists.

What is the best approach dealing this issue?

Should I try to create a new table and wrap it using try catch ?

Solution 1:

From reading the documentation, I can see that there are three methods by which you can check if a table exists.

1. The CreateTable API throws an error ResourceInUseException if the table already exists. Wrap the create_table method with try except to catch this
2. You can use the ListTables API to get the list of table names associated with the current account and endpoint. Check if the table name is present in the list of table names you get in the response.
3. The DescribeTable API will throw an error ResourceNotFoundException if the table name you request doesn't exist.

To me, the first option sounds better if you just want to create a table.

Edit: I see that some people are finding it difficult to catch the exceptions. I will put some code below for you to know how to handle exceptions in boto3.

Example 1

import boto3

dynamodb_client = boto3.client('dynamodb')

try:
    response = dynamodb_client.create_table(
        AttributeDefinitions=[
            {
                'AttributeName': 'Artist',
                'AttributeType': 'S',
            },
            {
                'AttributeName': 'SongTitle',
                'AttributeType': 'S',
            },
        ],
        KeySchema=[
            {
                'AttributeName': 'Artist',
                'KeyType': 'HASH',
            },
            {
                'AttributeName': 'SongTitle',
                'KeyType': 'RANGE',
            },
        ],
        ProvisionedThroughput={
            'ReadCapacityUnits': 5,
            'WriteCapacityUnits': 5,
        },
        TableName='test',
    )
except dynamodb_client.exceptions.ResourceInUseException:
    # do something here as you require
    pass

Example 2

import boto3

dynamodb_client = boto3.client('dynamodb')


table_name = 'test'
existing_tables = dynamodb_client.list_tables()['TableNames']

if table_name not in existing_tables:
    response = dynamodb_client.create_table(
        AttributeDefinitions=[
            {
                'AttributeName': 'Artist',
                'AttributeType': 'S',
            },
            {
                'AttributeName': 'SongTitle',
                'AttributeType': 'S',
            },
        ],
        KeySchema=[
            {
                'AttributeName': 'Artist',
                'KeyType': 'HASH',
            },
            {
                'AttributeName': 'SongTitle',
                'KeyType': 'RANGE',
            },
        ],
        ProvisionedThroughput={
            'ReadCapacityUnits': 5,
            'WriteCapacityUnits': 5,
        },
        TableName=table_name,
    )

Example 3

import boto3

dynamodb_client = boto3.client('dynamodb')

try:
    response = dynamodb_client.describe_table(TableName='test')
except dynamodb_client.exceptions.ResourceNotFoundException:
    # do something here as you require
    pass

Solution 2:

import boto3

from botocore.exceptions import ClientError

TABLE_NAME = "myTableName"
dynamodb = boto3.resource('dynamodb', endpoint_url="https://dynamodb.us-east-1.amazonaws.com")

table = dynamodb.Table(TABLE_NAME)

try:
    response = client.describe_table(TableName=TABLE_NAME)

except ClientError as ce:
if ce.response['Error']['Code'] == 'ResourceNotFoundException':
    print "Table " + TABLE_NAME + " does not exist. Create the table first and try again."
else:
    print "Unknown exception occurred while querying for the " + TABLE_NAME + " table. Printing full error:"
    pprint.pprint(ce.response)

Solution 3:

Alternate approach if you do not want to use boto3.client but only boto3.resource:

import boto3

database = boto3.resource('dynamodb', endpoint_url="http://localhost:8000")    

table_name  = 'MyTable'
table_names = [table.name for table in database.tables.all()]

if table_name in table_names:
    print('table', table_name, 'exists')