Lambda write & read DynamoDB

Writing and Reading from DynamoDB using Lambda Python

...using API Gateway as trigger.

Below is a simple example of writing to and reading from a DynamoDB table. This code would be triggered by a webpage that sends a JSON package via configured API Gateway. And it would return a JSON package back to the website. Be sure the Role has the necessary permission to read and write to DynamoDB table being used.

import json
import decimal
import boto3
from boto3.dynamodb.conditions import Key, Attr

# Helper class to convert a DynamoDB 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)

def lambda_handler(event, context):
    # TODO implement
    #define DynamoDB object
    dynamodb = boto3.resource('dynamodb')
    #define which table we want to use
    table = dynamodb.Table("yourOwnTable")
    #print the status of the table
    print(table.table_status)
    
    #Get the body string from the event input json
    #we convert this to json so we can use it easier
    body = json.loads(event['body'])
    #we enter this into the DB
    respose1 = table.put_item(
        Item={
            'RequestTime': body['myFormVariables']['RequestTime'],
            'User': body['myFormVariables']['User'],
            'entryID': body['myFormVariables']['entryID'],
            'Field1': body['myFormVariables']['Field2'],
            'Field2': body['myFormVariables']['Field1']
        }
    )

    print("Table Output")
    ##get it all
    response2 = table.scan()
    ##Get only the objects that match the given key
    #response = table.query(KeyConditionExpression=Key('entryID').eq("L3dVGMDS7yqzdoxCxOm4fg"))
    
    #Print all values in the response
    for i in response2['Items']:
        print(i['entryID'], ":", i['Field1'], ":", i['Field2'], ":", i['RequestTime'])
    
    #Just to illustrate how I handled cognito user information that was passed in
    cognito = event['requestContext']['authorizer']['claims']['cognito:username']
    
    return {
        'statusCode': 200,
        'body': json.dumps(response2, cls=DecimalEncoder)
    }

Test Sample

Here is a test event you can use to test your code. 

{
  "path": "/entry",
  "httpMethod": "POST",
  "headers": {
    "Accept": "*/*",
    "Authorization": "eyJraWQiOiLTzRVMWZs",
    "content-type": "application/json; charset=UTF-8"
  },
  "queryStringParameters": null,
  "pathParameters": null,
  "requestContext": {
    "authorizer": {
      "claims": {
        "cognito:username": "the_username"
      }
    }
  },
  "body": "{\"myFormVariables\":{
  \"RequestTime\":"2019-01-11T05:56:22.517Z\",
  \"User\":\"the_username\",
  \"entryID\":\"L3dVGMDS7yqzdoxCxOm4f1\",
  \"Field1\":47,
  \"Field2\":122}}"
}

Output