Conditional DynamoDB put item in lambda (python)

Question

How do I put an item in a dynamodb table only if that item does not exist. So far, I have:

table.put_item(
   Item:={
       'greeting': 'hi'
   },
   ConditionExpression= 'attribute_not_exists(hi)'
)

What would my condition expression be?

E.J. Brennan · Accepted Answer · 2020-08-25 20:31:23Z

1

It would be something like this:

ConditionExpression= "attribute_not_exists(Id)" // where id is your unique key

answered Aug 25, 2020 at 20:31

E.J. Brennan

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3 Comments

saragit Over a year ago

I just edited my question, however it is still not working. The item keeps getting overwritten,

hawschiat Over a year ago

You should replace hi in attribute_not_exists to the name of your partition key attribute e.g. attribute_not_exists(greeting) assuming "greeting" is the name of the partition key

hawschiat Over a year ago

You can catch the error with ClientError defined in the Boto3 SDK (See how), then add your error handling logic.

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