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#ask-ai
Title
# ask-ai
b

Brent Shulman

02/14/2024, 10:52 PM
Is there a way to define an assets inputs based on the partition?
s

Scout

02/14/2024, 10:52 PM
Yes, there is a way to define an asset's inputs based on the partition. The documentation provides an example of how to use the
asset_partitions_def_for_input
method within an asset to get the
PartitionsDefinition
for a particular input. This method can be used to log or otherwise act upon the partition information of an input asset within the body of another asset. Here's an example from the documentation:
Copy code
python from dagster import AssetExecutionContext, DailyPartitionsDefinition, asset  partitions_def = DailyPartitionsDefinition("2023-08-20")  @asset(partitions_def=partitions_def) def upstream_asset():     ...  @asset(partitions_def=partitions_def) def downstream_asset(context: AssetExecutionContext, upstream_asset):     <http://context.log.info|context.log.info>(context.asset_partitions_def_for_input("upstream_asset"))     # materializing the 2023-08-21 partition of this asset will log:     #   DailyPartitionsDefinition("2023-08-20")
In this example, both
upstream_asset
and
downstream_asset
are defined with the same
DailyPartitionsDefinition
. When the
downstream_asset
is materialized, it logs the
PartitionsDefinition
of the
upstream_asset
input, which is determined by the partition key of the run. This approach allows you to define how an asset's inputs should be handled based on the partition information, which can be particularly useful when dealing with partitioned assets and ensuring that the correct partitions are being used as inputs for downstream computations.
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