PynamoDB's Model.get operation throws an incorrect exception when getting an object with only single optional attribute_to_get #1287
Description
Hey,
I just ran into an issue while using Model.get API. I called it with a single attribute value in attributes_to_get parameter. This attribute in my model is an optional value, that might not exist on my DynamoDB object. So when the underlying get_item call is made, it returns a response where Item field is an empty dict ({}).
So then this if case is executed, which evaulates to false, and because of that, a DoesNotExist exception is thrown.
I would expect this API to return an empty object, or at least throw a different kind of exception. Though in my case, such a query is completely valid, so I would prefer an empty object response. I worked around it by requesting the attributes_to_get parameter with two values, my hash key attribute, and my optional attribute. That way I always get some value to deserialize into class instance.
What do you think? Do you think this is something that should be modified in PynamoDB?
A small sample to present what I mean
from pynamodb.attributes import (
UnicodeAttribute,
)
from pynamodb.models import Model
class SomeModel(Model):
id = UnicodeAttribute(hash_key=True)
optional_attr = UnicodeAttribute(null=True, default=None)
def get_optional_attr():
try:
# this throws an exception even if instance with hash_key 1 exists, but it doesn't contain a value for optional_attr.
return SomeModel.get("1", attr_name=["optional_attr"]).optional_attr
except Exception as e:
print(e)
return None
def get_optional_attr_with_default():
# This works fine, returning a None for optional_attr, but it also obtains the "id" attribute from DynamoDB.
return SomeModel.get("1", attr_name=["id", "optional_attr"]).optional_attr