Introduction to DynamoDB

Amazon DynamoDB is a fully managed NoSQL database service that provides fast and predictable performance with seamless scalability. It allows developers to store and retrieve any amount of data, at any scale, and serves as the backbone for many large-scale applications.

Getting Started with DynamoDB

Before diving into the API examples, ensure you have AWS SDKs installed in your application. The examples below use Python and the Boto3 library.

Creating a Table

  import boto3

  dynamodb = boto3.resource('dynamodb')
  table = dynamodb.create_table(
      TableName='Movies',
      KeySchema=[
          {
              'AttributeName': 'year',
              'KeyType': 'HASH'
          },
          {
              'AttributeName': 'title',
              'KeyType': 'RANGE'
          }
      ],
      AttributeDefinitions=[
          {
              'AttributeName': 'year',
              'AttributeType': 'N'
          },
          {
              'AttributeName': 'title',
              'AttributeType': 'S'
          }
      ],
      ProvisionedThroughput={
          'ReadCapacityUnits': 5,
          'WriteCapacityUnits': 5
      }
  )

  print("Table status:", table.table_status)

Adding an Item

  table = dynamodb.Table('Movies')
  table.put_item(
      Item={
          'year': 2015,
          'title': 'The Big New Movie',
          'info': {
              'plot': 'Nothing happens at all.',
              'rating': decimal.Decimal(0)
          }
      }
  )

Getting an Item

  response = table.get_item(
      Key={
          'year': 2015,
          'title': 'The Big New Movie'
      }
  )
  if 'Item' in response:
      print(response['Item'])
  else:
      print("Item not found.")

Updating an Item

  table.update_item(
      Key={
          'year': 2015,
          'title': 'The Big New Movie'
      },
      UpdateExpression='SET info.rating = :val1',
      ExpressionAttributeValues={
          ':val1': decimal.Decimal(5)
      }
  )

Deleting an Item

  table.delete_item(
      Key={
          'year': 2015,
          'title': 'The Big New Movie'
      }
  )

Building a Simple App with DynamoDB

Let’s put together a simple application using the APIs discussed. We’ll create a Python script to manage a movie collection database:

Code Example

  import boto3
  import decimal
  from boto3.dynamodb.conditions import Key

  def create_table(dynamodb=None):
      table = dynamodb.create_table(
          TableName='MoviesCollection',
          KeySchema=[
              {
                  'AttributeName': 'year',
                  'KeyType': 'HASH'
              },
              {
                  'AttributeName': 'title',
                  'KeyType': 'RANGE'
              }
          ],
          AttributeDefinitions=[
              {
                  'AttributeName': 'year',
                  'AttributeType': 'N'
              },
              {
                  'AttributeName': 'title',
                  'AttributeType': 'S'
              }
          ],
          ProvisionedThroughput={
              'ReadCapacityUnits': 5,
              'WriteCapacityUnits': 5
          }
      )
      return table

  def add_movie(year, title, plot, rating, dynamodb=None):
      table = dynamodb.Table('MoviesCollection')
      table.put_item(
          Item={
              'year': year,
              'title': title,
              'info': {
                  'plot': plot,
                  'rating': decimal.Decimal(rating)
              }
          }
      )

  def get_movie(year, title, dynamodb=None):
      table = dynamodb.Table('MoviesCollection')
      response = table.get_item(
          Key={
              'year': year,
              'title': title
          }
      )
      return response['Item'] if 'Item' in response else None

  if __name__ == '__main__':
      dynamodb = boto3.resource('dynamodb')
      movie_table = create_table(dynamodb)
      movie_table.wait_until_exists()

      add_movie(2021, 'A Great Movie', 'An epic film of great proportions.', 8.5, dynamodb)
      movie = get_movie(2021, 'A Great Movie', dynamodb)
      print(movie)

This script creates a DynamoDB table, adds a movie item, and retrieves the movie details. You can expand this application by adding more functions like updating and deleting items, listing all movies, etc.

This guide provides a foundation for working with DynamoDB in Python. Dive into the AWS documentation for more detailed information on each API and advanced features.

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