How can you query an item in a list field in DynamoDB using Python?

Question

I have a table that contains an item with the following attributes:

{
  "country": "USA",
  "names": [
    "josh",
    "freddy"
  ],
  "phoneNumber": "123",
  "userID": 0
}

I'm trying to query an item in a DynameDB by looking for a name using python. So I would write in my code that the item I need has "freddy" in the field "names".

I saw many forums mentioning "contains" but none that show an example...

My current code is the following:

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('users_table')
data = table.query(
    FilterExpression: 'names = :name',
    ExpressionAttributeValues: {
      ":name": "freddy"
    }
)

I obviously cannot use that because "names" is a list and not a string field. How can I look for "freddy" in names?

jellycsc · Accepted Answer · 2020-07-14 03:16:44Z

3

Since names field isn't part of the primary key, so you can't use query. The only way to look for an item by names is to use scan.

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

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('users_table')
data = table.scan(
    FilterExpression=Attr('names').contains('freddy')
)

answered Jul 14, 2020 at 3:16

jellycsc

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3 Comments

Michel Chalfoun Over a year ago

I tried this and i’m now getting Attr is not defined...

Michel Chalfoun Over a year ago

[ERROR] NameError: name 'Attr' is not defined

jellycsc Over a year ago

from boto3.dynamodb.conditions import Key, Attr

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