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Boto3 list_append a value to overwrite a null value in a list


Boto3, python and how to handle errorsIs it possible to combine if_not_exists and list_append in update_itemIncrementing Number Property in AWS DynamoDB Objective CWhy does my AWS Lambda script return 'Instances' instead of the instance ID?dynamoDB update-item python boto3"EndpointConnectionError : unable to connect to endpoint https://lambda-xyz/wehwk.comLimit on Number of Attributes in Table DynamoDB?Lambda function blanks DynamoDB valuesAWS is complaining about a parameter being the wrong type, when it really is notC# serialize DynamoDB item to JSON






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0















I am writing a small lambda function to update a game item in my DynamoDB. My game item has a participants attribute which is a list consisting of the participant_id of each participant in the game. When a game doesn't have any participants yet (i.e. a round later in the bracket) the list will hold 2 null values:



Empty participant list



I would like to overwrite the null values with a string each time I add a new participant. Currently I am able to append a new String to the list but the null values remain:



After adding a participant



How can I overwrite one of the 2 null values with a string using boto3?
(i.e. to where it looks like ["participantOneId", Null] after adding one participant and ["participantOneId", "participantTwoId"] after adding both participants)
This is my current implementation:



import boto3
import json

dynamodb = boto3.resource("dynamodb")
gamesTable = dynamodb.Table('games')

def lambda_handler(event, context):
# get "next_game_id" and "winner_id" from the event body
updated_next_game = gamesTable.update_item(
Key='id': next_game_id ,
UpdateExpression="SET participants = list_append(participants, :i)",
ExpressionAttributeValues=
':i': [winner_id],
,
ReturnValues="ALL_NEW"
)









share|improve this question






















  • Why store two Null values in the first place?

    – jarmod
    Mar 8 at 23:42











  • Good point @jarmod

    – Andrew A.
    Mar 11 at 17:16

















0















I am writing a small lambda function to update a game item in my DynamoDB. My game item has a participants attribute which is a list consisting of the participant_id of each participant in the game. When a game doesn't have any participants yet (i.e. a round later in the bracket) the list will hold 2 null values:



Empty participant list



I would like to overwrite the null values with a string each time I add a new participant. Currently I am able to append a new String to the list but the null values remain:



After adding a participant



How can I overwrite one of the 2 null values with a string using boto3?
(i.e. to where it looks like ["participantOneId", Null] after adding one participant and ["participantOneId", "participantTwoId"] after adding both participants)
This is my current implementation:



import boto3
import json

dynamodb = boto3.resource("dynamodb")
gamesTable = dynamodb.Table('games')

def lambda_handler(event, context):
# get "next_game_id" and "winner_id" from the event body
updated_next_game = gamesTable.update_item(
Key='id': next_game_id ,
UpdateExpression="SET participants = list_append(participants, :i)",
ExpressionAttributeValues=
':i': [winner_id],
,
ReturnValues="ALL_NEW"
)









share|improve this question






















  • Why store two Null values in the first place?

    – jarmod
    Mar 8 at 23:42











  • Good point @jarmod

    – Andrew A.
    Mar 11 at 17:16













0












0








0








I am writing a small lambda function to update a game item in my DynamoDB. My game item has a participants attribute which is a list consisting of the participant_id of each participant in the game. When a game doesn't have any participants yet (i.e. a round later in the bracket) the list will hold 2 null values:



Empty participant list



I would like to overwrite the null values with a string each time I add a new participant. Currently I am able to append a new String to the list but the null values remain:



After adding a participant



How can I overwrite one of the 2 null values with a string using boto3?
(i.e. to where it looks like ["participantOneId", Null] after adding one participant and ["participantOneId", "participantTwoId"] after adding both participants)
This is my current implementation:



import boto3
import json

dynamodb = boto3.resource("dynamodb")
gamesTable = dynamodb.Table('games')

def lambda_handler(event, context):
# get "next_game_id" and "winner_id" from the event body
updated_next_game = gamesTable.update_item(
Key='id': next_game_id ,
UpdateExpression="SET participants = list_append(participants, :i)",
ExpressionAttributeValues=
':i': [winner_id],
,
ReturnValues="ALL_NEW"
)









share|improve this question














I am writing a small lambda function to update a game item in my DynamoDB. My game item has a participants attribute which is a list consisting of the participant_id of each participant in the game. When a game doesn't have any participants yet (i.e. a round later in the bracket) the list will hold 2 null values:



Empty participant list



I would like to overwrite the null values with a string each time I add a new participant. Currently I am able to append a new String to the list but the null values remain:



After adding a participant



How can I overwrite one of the 2 null values with a string using boto3?
(i.e. to where it looks like ["participantOneId", Null] after adding one participant and ["participantOneId", "participantTwoId"] after adding both participants)
This is my current implementation:



import boto3
import json

dynamodb = boto3.resource("dynamodb")
gamesTable = dynamodb.Table('games')

def lambda_handler(event, context):
# get "next_game_id" and "winner_id" from the event body
updated_next_game = gamesTable.update_item(
Key='id': next_game_id ,
UpdateExpression="SET participants = list_append(participants, :i)",
ExpressionAttributeValues=
':i': [winner_id],
,
ReturnValues="ALL_NEW"
)






amazon-web-services aws-lambda amazon-dynamodb boto3






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 8 at 23:27









Andrew A.Andrew A.

440714




440714












  • Why store two Null values in the first place?

    – jarmod
    Mar 8 at 23:42











  • Good point @jarmod

    – Andrew A.
    Mar 11 at 17:16

















  • Why store two Null values in the first place?

    – jarmod
    Mar 8 at 23:42











  • Good point @jarmod

    – Andrew A.
    Mar 11 at 17:16
















Why store two Null values in the first place?

– jarmod
Mar 8 at 23:42





Why store two Null values in the first place?

– jarmod
Mar 8 at 23:42













Good point @jarmod

– Andrew A.
Mar 11 at 17:16





Good point @jarmod

– Andrew A.
Mar 11 at 17:16












1 Answer
1






active

oldest

votes


















0














If you don't need to append anything to the list, then you don't want to use list_append. Something like this should work fine:



UpdateExpression="SET participants[0] = <whatever>"


and/or



UpdateExpression="SET participants[1] = <whatever>"


(If you won't know in advance which of the two elements you need to set, you can always use if_not_exists.)






share|improve this answer























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    1 Answer
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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0














    If you don't need to append anything to the list, then you don't want to use list_append. Something like this should work fine:



    UpdateExpression="SET participants[0] = <whatever>"


    and/or



    UpdateExpression="SET participants[1] = <whatever>"


    (If you won't know in advance which of the two elements you need to set, you can always use if_not_exists.)






    share|improve this answer



























      0














      If you don't need to append anything to the list, then you don't want to use list_append. Something like this should work fine:



      UpdateExpression="SET participants[0] = <whatever>"


      and/or



      UpdateExpression="SET participants[1] = <whatever>"


      (If you won't know in advance which of the two elements you need to set, you can always use if_not_exists.)






      share|improve this answer

























        0












        0








        0







        If you don't need to append anything to the list, then you don't want to use list_append. Something like this should work fine:



        UpdateExpression="SET participants[0] = <whatever>"


        and/or



        UpdateExpression="SET participants[1] = <whatever>"


        (If you won't know in advance which of the two elements you need to set, you can always use if_not_exists.)






        share|improve this answer













        If you don't need to append anything to the list, then you don't want to use list_append. Something like this should work fine:



        UpdateExpression="SET participants[0] = <whatever>"


        and/or



        UpdateExpression="SET participants[1] = <whatever>"


        (If you won't know in advance which of the two elements you need to set, you can always use if_not_exists.)







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Mar 11 at 19:51









        B. ShefterB. Shefter

        429111




        429111





























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