Whis this works? using reduce to accumulate filter expressions

[daviwesley]

My question is about the And class used on filter expressions on dynamodb , can you guys explain why this is work?

import boto3
from boto3.dynamodb.conditions import And, Key

dynamodb = boto3.resource("dynamodb")
table = dynamodb.Table("anytable")
filters = {"status": "paid"}
table.scan(FilterExpression=reduce(And, ([Key(k).eq(v) for k, v in filters.items()])))

[aBurmeseDev]

Hi @daviwesley - thanks for reaching out.

Could you please elaborate the use case you're trying to accomplish? From my initial research on FilterExpression, AND isn't one of the operators listed but I could reach out to service team (DynamoDB) on your behalf if you could share what you're looking to use the expression for.

The syntax for a filter expression is similar to that of a key condition expression. Filter expressions can use the same comparators, functions, and logical operators as a key condition expression. In addition, filter expressions can use the not-equals operator (<>), the OR operator, the CONTAINS operator, the IN operator, the BEGINS_WITH operator, the BETWEEN operator, the EXISTS operator, and the SIZE operator.

I'll link a few docs for reference:

• https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.FilterExpression.html
• https://boto3.amazonaws.com/v1/documentation/api/latest/reference/customizations/dynamodb.html#ref-dynamodb-conditions

[daviwesley]

Basically the main purpose is to chain various & operator on the fields, so instead of doing by hand the reduce function construct this functionality

[daviwesley]

I also updated my snippet code, u can see that And is a valid condition