Error: dynamodb property projection cannot be empty

What's Causing This Error

This error message indicates that the ProjectionExpression property of the 'Scan' or 'Query' operation is empty or not set. The ProjectionExpression is used to specify the attributes that need to be returned from an item.

If you have provided the ProjectionExpression parameter and have given an empty string, you will run into this error.

Solution: Here's How To Resolve It

To solve this error, provide a value for the ProjectionExpression property. Generally, you can define the name of the attributes you wish to project in the operation.

Here is an example of how to perform a scan operation with a valid 'ProjectionExpression':

import boto3

# Instantiate a client
dynamodb = boto3.client('dynamodb', region_name='us-west-2')

# Define the parameters
table_name = "my_table"
projection_expression = "attribute1, attribute2"

# Perform the operation
response = dynamodb.scan(TableName=table_name,
             ProjectionExpression=projection_expression)
print(response)

You can also use ExpressionAttributeNames to provide an alias for your attribute names.

import boto3

# Instantiate a client
dynamodb = boto3.client('dynamodb', region_name='us-west-2')

# Define the parameters
table_name = "my_table"
projection_expression = "#a1, #a2"
expression_attribute_names = {"#a1": "attribute1", "#a2": "attribute2"}

# Perform the operation
response = dynamodb.scan(TableName=table_name, ProjectionExpression=projection_expression,
             ExpressionAttributeNames=expression_attribute_names)
print(response)