Error: Float types are not supported. Use decimal types instead.

Float types are not supported. Use decimal types instead. comes from boto3's DynamoDB serializer. It accepts Decimal and integer numbers but rejects Python float values, including floats nested inside lists or dictionaries.

from decimal import Decimal
import boto3
import json

table = boto3.resource("dynamodb").Table("Products")
table.put_item(Item={"pk": "product-1", "price": Decimal("30.51")})

item = json.loads('{"pk":"product-2","price":30.51}', parse_float=Decimal)
table.put_item(Item=item)

Parse the original decimal text when possible. Decimal(30.51) preserves the binary float approximation; Decimal(str(value)) is a practical conversion when a float already exists, but cannot recover precision previously lost. Inspect nested structures for remaining floats.

Converting a price to str merely to bypass the error stores a DynamoDB String and changes numeric comparisons and arithmetic. Use strings only when that is the intended model. Non-finite values such as infinity and NaN are not valid DynamoDB numbers.

See Python examples and AWS documentation.