Boto DynamoDB: How to prevent items from being overwritten with batch_write?

I am using boto DynamoDB v2 and I am writing items to a table in batch. However, I cannot prevent DynamoDB from overwriting the attributes of existing elements. I would prefer the process to fail.

The table has the following schema:

from boto.dynamodb2.table import Table, HashKey, RangeKey

conn = get_connection()
t = Table.create(
        'intervals',
        schema=[
            HashKey('id'),
            RangeKey('start')
        ],
        connection=conn
    )

      

        
        
        
      

    

Let's say I insert one element:

item = {
    'id': '4920',
    'start': '20',
    'stop': '40'
}
t.put_item(data=item)

      

        
        
        
      

    

Now when I insert new items with batch_write

, I want to make sure DynamoDB doesn't overwrite the existing item. According to the documentation , this should be achieved with a parameter overwrite

from the put_item

class method BatchTable

(which is the one used as the context manager in the example below)

new_items = [{
    'id': '4920',
    'start': '20',
    'stop': '90'
}]

with t.batch_write() as batch:
    for i in new_items:
        batch.put_item(data=i, overwrite=False)

      

        
        
        
      

    

However, it is not. The attribute stop

in my example gets a new value 90

. Thus, the previous value ( 40

) is overwritten.

If I use my own table method the put_item

parameter works overwrite

. By setting it to True

, instead of the value, the stop

value False

is printed to ConditionalCheckFailedException

.

How can I get this exception when used batch_write

?