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# ask-ai
g

Giacomo Colombo

03/13/2024, 4:34 PM
How to load all assets but 2, instead of all assets?
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all_assets = load_assets_from_modules([
    my_module_with_assets])
s

Scout

03/13/2024, 4:34 PM
To load all assets except for two specific assets, you can use the
load_assets_from_modules
function in combination with asset selection tools provided by Dagster. The
load_assets_from_modules
function will load all assets from the specified modules, and then you can use
AssetSelection
to exclude the assets you don't want to include. Here's an example of how you might do this, assuming you know the keys of the assets you want to exclude:
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python from dagster import load_assets_from_modules, AssetSelection  # Load all assets from the specified module all_assets = load_assets_from_modules([my_module_with_assets])  # Define the keys of the assets you want to exclude assets_to_exclude = {"asset_key_to_exclude_1", "asset_key_to_exclude_2"}  # Use AssetSelection to filter out the assets you don't want selected_assets = [     asset for asset in all_assets if asset.key not in assets_to_exclude ]  # Now selected_assets contains all assets except for the two you excluded
In this example,
asset_key_to_exclude_1
and
asset_key_to_exclude_2
are the keys of the assets you want to exclude. The
AssetSelection
utility is used to create a list of assets that excludes the specified assets by their keys. Please note that the example above assumes that you have a way to iterate over the loaded assets and access their keys. If the
load_assets_from_modules
function does not return an iterable collection of assets or if the assets do not have a
key
attribute, you would need to adjust the approach accordingly. Remember to replace
asset_key_to_exclude_1
and
asset_key_to_exclude_2
with the actual keys of the assets you wish to exclude.
g

Giacomo Colombo

03/13/2024, 5:08 PM
@Scout my problem is that if i try to filter all_asssets in whatever way, I get an error related to the presence of multi_asset methods this line:
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selected_assets = [
    asset for asset in all_assets if asset.key not in assets_to_exclude
]
return the error: dagster._check.CheckError: Invariant failed. Description: Tried to retrieve asset key from an assets definition with multiple asset keys: ["buses_asset"], ["autobus_filobus_km_asset"], ["tram_metro_km_asset"], ["car_sharing_asset"], ["bike_sharing_asset"] these are my asset created from a multi_asset method and passed to other asset as dependencies via AssetKey. How to fix this?
s

Scout

03/13/2024, 5:08 PM
The error you're encountering indicates that you're trying to access the
key
attribute on an asset definition that represents multiple assets, which is not possible because a multi-asset definition does not have a single
key
attribute. In Dagster, when you define multiple assets within a single
@multi_asset
decorator, you're creating a collection of assets that are grouped together. To work with these assets individually, you need to handle them differently than you would with single assets. To exclude specific assets from a multi-asset definition, you can use the
AssetSelection
API to create a selection that includes all assets except the ones you want to exclude. Here's an example of how you might do this:
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python from dagster import AssetSelection  # Assuming you have a list of asset keys you want to exclude assets_to_exclude = [AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")]  # Create an asset selection that excludes the specified assets selected_assets = AssetSelection.all() - AssetSelection.keys(*assets_to_exclude)
In this example,
AssetSelection.all()
creates a selection that includes all assets, and then we subtract the assets we want to exclude using
AssetSelection.keys(*assets_to_exclude)
. This will give you a new selection that includes all assets except for the ones with the specified keys. Please note that the
AssetSelection
API is used to create selections of assets for use in jobs and other contexts where you need to specify which assets to work with. The actual usage of
AssetSelection
may vary depending on your specific use case and the context in which you're trying to load or execute assets. If you're still encountering issues, please provide more details about the context in which you're trying to load and filter assets, and I can provide more targeted guidance.
g

Giacomo Colombo

03/13/2024, 5:13 PM
@Scout No because I need to pass the selected_asset to a dagster Defintion that expect type 'Iterable[AssetsDefinition | SourceAsset | CacheableAssetsDefinition] | None', got 'SubtractAssetSelection' instead
s

Scout

03/13/2024, 5:13 PM
I apologize for the confusion. It seems that the
AssetSelection
API does not directly return an iterable of asset definitions that can be passed to a
Definitions
object. Instead, it is used for selecting assets within the context of a job or other execution contexts. Given that you need to pass an iterable of asset definitions to a
Definitions
object and you want to exclude certain assets from a multi-asset definition, you will need to take a different approach. One way to handle this is to define your assets individually or in smaller groups that can be more easily included or excluded based on your needs. If you have control over the asset definitions, consider refactoring the multi-asset definitions into separate
@asset
definitions or smaller
@multi_asset
groups that can be selectively included. If refactoring is not an option, you may need to create a custom function that can filter out the assets you want to exclude from the iterable of asset definitions. This function would need to inspect each asset definition, determine if it represents a single asset or multiple assets, and then include or exclude it based on your criteria. Unfortunately, without a built-in way to filter multi-asset definitions in the manner you're describing, the solution will likely involve some custom logic specific to your asset structure and the way they are defined in your codebase. If you continue to face difficulties, I recommend reaching out to the Dagster community or support channels with details about your specific asset definitions and the structure of your code. They may be able to provide more context-specific advice or suggest an alternative approach that aligns with the capabilities of the current version of Dagster.
g

Giacomo Colombo

03/13/2024, 5:15 PM
@Scout it is not simpler to store in the new "selected_assets" the ones with multiasset first, and then perform the list_comprehnsion that return the error
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selected_assets = [
    asset for asset in all_assets if asset.key not in assets_to_exclude
]
s

Scout

03/13/2024, 5:15 PM
Indeed, if you have a mix of single and multi-assets, you would need to handle them differently when creating your
selected_assets
list. The
asset.key
attribute is not available for multi-assets, as they represent multiple asset keys. Here's a strategy you can use to create a
selected_assets
list that includes multi-assets and excludes certain single assets: 1. Separate your multi-assets from single assets. 2. Filter out the single assets you want to exclude. 3. Combine the multi-assets with the filtered single assets. Here's an example of how you might implement this:
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python # Assuming all_assets is a list of both single and multi-asset definitions multi_assets = [asset for asset in all_assets if hasattr(asset, 'asset_keys')] single_assets = [asset for asset in all_assets if not hasattr(asset, 'asset_keys')]  # Define the keys of the assets you want to exclude assets_to_exclude = {AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")}  # Filter out the single assets you want to exclude filtered_single_assets = [     asset for asset in single_assets if asset.key not in assets_to_exclude ]  # Combine multi-assets with the filtered single assets selected_assets = multi_assets + filtered_single_assets
In this example,
multi_assets
is a list of asset definitions that represent multiple assets, and
single_assets
is a list of asset definitions that represent a single asset. We then filter the single assets to exclude the ones with keys in
assets_to_exclude
and combine them with the multi-assets to create the
selected_assets
list. This approach should give you a list of asset definitions that can be passed to a
Definitions
object without encountering the error related to multi-asset methods. Remember to replace
"asset_key_to_exclude_1"
and
"asset_key_to_exclude_2"
with the actual keys of the assets you wish to exclude.
g

Giacomo Colombo

03/13/2024, 5:18 PM
@Scout no the error is still the same! dagster._check.CheckError: Invariant failed. Description: Tried to retrieve asset key from an assets definition with multiple asset keys: ["buses_asset"], ["autobus_filobus_km_asset"], ["tram_metro_km_asset"], ["car_sharing_asset"], ["bike_sharing_asset"]
s

Scout

03/13/2024, 5:18 PM
I apologize for the confusion earlier. It seems that the approach I suggested did not resolve the issue with multi-assets. Given the error message you're encountering, it appears that Dagster is expecting an
AssetsDefinition
object, but it's encountering a situation where it's trying to retrieve a single asset key from a definition that includes multiple asset keys. To properly exclude certain assets from a collection that includes multi-assets, you'll need to ensure that you're working with the
AssetsDefinition
objects correctly. Unfortunately, the documentation does not provide a direct example of filtering assets from a list that includes multi-assets. Since the error persists and the documentation does not provide a clear solution, I recommend reaching out to the Dagster community or support channels for assistance. They may have encountered similar issues and can provide guidance specific to your use case. In the meantime, you can also try to debug the issue by inspecting the
all_assets
list to understand the structure of the
AssetsDefinition
objects it contains, especially those that represent multiple assets. This might give you more insight into how to properly exclude the assets you don't want without triggering the error.
g

Giacomo Colombo

03/13/2024, 5:20 PM
@Scout this simply return an empty list.
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multi_assets = [asset for asset in all_assets if hasattr(asset, 'asset_keys')]
There is another way to check if it is a multi_asset?
s

Scout

03/13/2024, 5:20 PM
In Dagster, multi-assets are defined using the
@multi_asset
decorator, which allows you to define multiple assets at once. However, once these assets are loaded into memory, they are represented as instances of
AssetsDefinition
. To determine whether an
AssetsDefinition
instance represents a single asset or multiple assets, you can check the
asset_keys
attribute. If the
asset_keys
attribute is present and has more than one
AssetKey
, it indicates that the
AssetsDefinition
represents multiple assets. However, if the
asset_keys
attribute is not present or is not the correct way to check for multi-assets, you may need to use a different approach. One way to check if an
AssetsDefinition
is a multi-asset is to look at the
op
attribute, which should be an instance of a multi-asset operation if it is indeed a multi-asset. Here's how you might do that:
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python from dagster import MultiDependencyDefinition  multi_assets = [     asset for asset in all_assets     if isinstance(asset.op, MultiDependencyDefinition) ]
This code snippet checks if the
op
attribute of each asset is an instance of
MultiDependencyDefinition
, which is used internally by Dagster to represent a multi-asset operation. If this approach does not work, it's possible that the internal representation of assets in Dagster has changed, or there may be a more appropriate way to distinguish between single and multi-assets. In that case, consulting the latest Dagster documentation or reaching out to the Dagster community for support would be the best course of action. They may provide updated guidance on how to handle multi-assets in the version of Dagster you are using.
g

Giacomo Colombo

03/13/2024, 5:24 PM
@Scout what is the op attribute?? the error still persist!!! it does not work here is my asset:
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@multi_asset(
    outs={
        "buses_asset": AssetOut(),
        "autobus_filobus_km_asset": AssetOut(),
        "tram_metro_km_asset": AssetOut(),
        "car_sharing_asset": AssetOut(),
        "bike_sharing_asset": AssetOut(),
    },
)
def my_method_that_generates_multi_asset(context):
    do_something()
s

Scout

03/13/2024, 5:24 PM
I apologize for the confusion earlier. It seems there was a misunderstanding regarding the internal representation of multi-assets in Dagster. Given the
@multi_asset
decorator in your code snippet, you have defined a multi-asset. When you load assets using
load_assets_from_modules
, it should return an iterable of
AssetsDefinition
objects, which can represent either single assets or multi-assets. To filter out specific assets from this collection, you need to handle multi-assets differently since they don't have a single
asset.key
. Instead, you can check for the presence of multiple keys within the
AssetsDefinition
object. Here's an updated approach to filter out specific assets: 1. Identify the keys of the assets you want to exclude. 2. Iterate over the loaded assets and check if they are multi-assets. 3. If they are multi-assets, check if any of their keys are in the exclusion list. 4. If they are single assets, check their key against the exclusion list. Here's how you might implement this:
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python from dagster import AssetKey  # Define the keys of the assets you want to exclude assets_to_exclude = {AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")}  # Function to check if an asset definition is a multi-asset def is_multi_asset(asset_def):     return hasattr(asset_def, 'asset_keys') and len(asset_def.asset_keys) > 1  # Function to check if an asset (or any in a multi-asset) should be excluded def should_exclude_asset(asset_def, exclude_keys):     if is_multi_asset(asset_def):         # Check if any of the multi-asset's keys are in the exclude list         return any(key in exclude_keys for key in asset_def.asset_keys)     else:         # Check if the single asset's key is in the exclude list         return asset_def.key in exclude_keys  # Filter assets selected_assets = [     asset for asset in all_assets if not should_exclude_asset(asset, assets_to_exclude) ]
Please replace
"asset_key_to_exclude_1"
and
"asset_key_to_exclude_2"
with the actual keys of the assets you wish to exclude. If this approach still does not work, it may be necessary to consult the latest Dagster documentation or seek assistance from the Dagster community. The internal APIs and representations can change between versions, and they may provide the most up-to-date method for handling this situation.
g

Giacomo Colombo

03/13/2024, 5:31 PM
@Scout NO! it does not work! I can avoid to load in the first place the module that contain multi_asset, than exclude the single assets that I dont want, and then add the module with multi_asset in the new list of assets. how to do this last part to add another loaded module to my "selected_assets "
s

Scout

03/13/2024, 5:31 PM
If you want to avoid loading the module containing the multi-assets in the first place, you can load the other modules separately, exclude the single assets you don't want, and then load the module with the multi-assets and add them to your list of selected assets. Here's how you can do it step by step: 1. Load the modules that do not contain the multi-assets and exclude the single assets you don't want. 2. Load the module that contains the multi-assets. 3. Combine the assets from step 1 and step 2 into a single list. Here's an example of how you might implement this:
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python from dagster import load_assets_from_modules  # Load assets from modules that do not contain the multi-assets selected_assets = load_assets_from_modules([module_without_multi_assets])  # Define the keys of the single assets you want to exclude assets_to_exclude = {AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")}  # Filter out the single assets you want to exclude selected_assets = [     asset for asset in selected_assets if asset.key not in assets_to_exclude ]  # Load the module that contains the multi-assets multi_asset_module_assets = load_assets_from_modules([my_module_with_multi_assets])  # Add the multi-assets to the list of selected assets selected_assets.extend(multi_asset_module_assets)  # Now selected_assets contains all the assets you want, including the multi-assets
In this example, replace
module_without_multi_assets
with the actual module or modules you want to load that do not contain the multi-assets. Replace
my_module_with_multi_assets
with the actual module that contains the multi-assets. Also, replace
"asset_key_to_exclude_1"
and
"asset_key_to_exclude_2"
with the actual keys of the single assets you wish to exclude. This approach allows you to control exactly which assets are loaded and included in your
selected_assets
list. If you encounter any issues with this approach, please ensure that you are using the correct module names and asset keys, and consult the latest Dagster documentation for any updates or changes to the asset loading API.
g

Giacomo Colombo

03/13/2024, 5:43 PM
@Scout no nothing works!!! There is another way to just remove the unwanted assets from all_assets loaded? without filtering all assets?
s

Scout

03/13/2024, 5:43 PM
I apologize for the confusion and the trouble you're experiencing. If you're looking to remove unwanted assets from the
all_assets
list without filtering all assets, and you're encountering issues with multi-assets, you might want to consider using the
AssetGroup
API to explicitly construct an asset group with only the assets you want. Here's a general approach to how you might do this: 1. Load all assets from the module. 2. Create a new
AssetGroup
with only the assets you want to include. Here's an example of how you might implement this:
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python from dagster import load_assets_from_modules, AssetGroup, AssetKey  # Load all assets from the module all_assets = load_assets_from_modules([my_module_with_assets])  # Define the keys of the assets you want to exclude assets_to_exclude = {AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")}  # Create a new AssetGroup with only the assets you want to include selected_asset_group = AssetGroup(     asset for asset in all_assets if asset.key not in assets_to_exclude )  # Now selected_asset_group contains all the assets except for the ones you excluded
In this example, replace
"asset_key_to_exclude_1"
and
"asset_key_to_exclude_2"
with the actual keys of the assets you wish to exclude. Please note that this approach assumes that
all_assets
is a list of
AssetDefinition
objects and that each asset has a
key
attribute that can be used to identify it. If this is not the case, or if you're still encountering issues, it may be necessary to take a different approach. Given the persistent issues, it might be best to reach out to the Dagster community or support channels for further assistance. They may have more context-specific advice or alternative solutions that are better suited to your particular setup and the version of Dagster you are using.
g

Giacomo Colombo

03/13/2024, 5:59 PM
@Scout no! The problem is in the list comprehension as before!
s

Scout

03/13/2024, 5:59 PM
I apologize for the confusion. If you're encountering issues with list comprehensions due to multi-assets, and you want to avoid loading certain assets, you can take a different approach by using the
assets
parameter of
load_assets_from_modules
to explicitly specify which assets you want to load. Here's how you can do it: 1. Load all assets from the module except the multi-assets. 2. Explicitly load the multi-assets from the module. 3. Combine the two sets of assets. Here's an example of how you might implement this:
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python from dagster import load_assets_from_modules, AssetKey  # Load assets from modules that do not contain the multi-assets # and exclude the single assets you don't want assets_to_exclude = {AssetKey("asset_key_to_exclude_1"), AssetKey("asset_key_to_exclude_2")} selected_assets = load_assets_from_modules(     [module_without_multi_assets],     assets=lambda asset: asset.key not in assets_to_exclude )  # Load the module that contains the multi-assets multi_asset_module_assets = load_assets_from_modules([my_module_with_multi_assets])  # Combine the assets from both modules into a single list selected_assets.extend(multi_asset_module_assets)  # Now selected_assets contains all the assets you want, including the multi-assets
In this example, replace
module_without_multi_assets
with the actual module or modules you want to load that do not contain the multi-assets. Replace
my_module_with_multi_assets
with the actual module that contains the multi-assets. Also, replace
"asset_key_to_exclude_1"
and
"asset_key_to_exclude_2"
with the actual keys of the single assets you wish to exclude. This approach allows you to control exactly which assets are loaded and included in your
selected_assets
list. If you encounter any issues with this approach, please ensure that you are using the correct module names and asset keys, and consult the latest Dagster documentation for any updates or changes to the asset loading API.
g

Giacomo Colombo

03/18/2024, 5:54 PM
@Scout How to describe what is the unique Definitions repository in my README.md explaining some peculiarities and diffrence from old "repositories". how to say in an appropriate manner that everything you see in dagit need to be defined there to be considered by the dagster program.
s

Scout

03/18/2024, 5:54 PM
When updating your
README.md
to describe the transition from the old "repositories" to the new
Definitions
repository in Dagster, you'll want to clearly communicate the changes and their implications for users. Here's a suggested way to describe it: --- ## Transition to Definitions in Dagster In recent updates, Dagster has introduced a significant change in how we organize and manage our code. The concept of "repositories" has been replaced by a single, unique
Definitions
object. This change simplifies the structure and improves the clarity of our code organization within Dagster. ### What is Definitions?
Definitions
is a new, streamlined way to define all the components that make up your Dagster project. It is a single object that contains all the definitions defined within a code location. Definitions include assets, jobs, resources, schedules, and sensors. ### Key Peculiarities and Differences - Single Entry Point: There can only be one
Definitions
object per code location, whereas before, there could be multiple repositories within the same code location. - Explicit Organization: Everything that you want to appear in Dagit—the Dagster UI—must be defined within this
Definitions
object. If an asset or job is not included in
Definitions
, Dagster will not recognize it. - Simplified Hierarchy: The
Definitions
object removes the need for multiple layers of hierarchy, reducing confusion and making it easier for new users to understand the structure of their data pipelines. - Automatic Discovery: Dagster tools will automatically discover the
Definitions
object in a module. This object can be named anything and does not require a specific decorator like
@repository
. ### Example Usage Here's a simple example of how to define a
Definitions
object:
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python
from dagster import Definitions, asset

@asset
def my_asset():
    # Asset logic here

defs = Definitions(
    assets=[my_asset],
    # Include other definitions such as resources, schedules, and sensors here
)
### Implications for Dagit With the introduction of
Definitions
, Dagit now relies on this single object to load and display all the components of your Dagster project. This means that for any component to be visible and usable within Dagit, it must be included in the
Definitions
object. ### Migration from Old Repositories If you are migrating from the old repository system, you will need to consolidate your definitions into a single
Definitions
object. This process involves moving all assets, jobs, and other definitions from your
@repository
-decorated functions into the
Definitions
object. For more detailed migration steps and assistance, please refer to the official Dagster documentation or reach out to the Dagster community for s
upport. --- This description provides an overview of the changes and guides users on what to expect when interacting with the new
Definitions
object in Dagster. Adjust the content as necessary to fit the specifics of your project and the level of detail you wish to provide.
g

Giacomo Colombo

03/18/2024, 6:20 PM
@Scout ok but how to referr to the Defintions object in various way ? like repository or hub
s

Scout

03/18/2024, 6:20 PM
In your
README.md
, when referring to the
Definitions
object, you can use various terms that convey its role as the central place for organizing and managing all the components of your Dagster project. Here are some ways you can refer to the
Definitions
object: 1. Central Hub: You can describe the
Definitions
object as the central hub of your Dagster project, where all the components such as assets, jobs, schedules, and sensors are registered and managed. 2. Project Backbone: The
Definitions
object can be seen as the backbone of your project, providing the structure and organization necessary for Dagster to understand and execute your data pipelines. 3. Unified Registry: You might refer to the
Definitions
object as a unified registry that holds all the definitions in one place, streamlining the setup and maintenance of your project. 4. Single Source of Truth: The
Definitions
object serves as the single source of truth for what is included in your Dagster project and what will be recognized by Dagit and other Dagster tooling. 5. Configuration Core: As the core of your project's configuration, the
Definitions
object encapsulates all the necessary components that define the behavior and execution of your pipelines. 6. Definition Repository: Although the term "repository" has been used in the past, you can still use it in a more generic sense to describe the
Definitions
object as the repository of all your Dagster definitions. 7. Asset Collection: If your project is heavily centered around assets, you might refer to the
Definitions
object as the collection or catalog of all your assets. When using these terms, it's important to provide context to ensure that users understand that you are referring to the new
Definitions
object in Dagster. Here's an example of how you might use these terms in your `README.md`: --- In Dagster, the
Definitions
object acts as the central hub for our project, serving as the unified registry for all our assets, jobs, and operational definitions. This single source of truth is crucial for the organization and execution of our data pipelines, ensuring that everything is recognized and executable by Dagit and other Dagster tools. As we transition away from the older "repositories" concept, it's important to understand that the
Definitions
object is not just a new name—it's a reimagined configuration core that simplifies and enhances the way we work with Dagster. --- By using these various terms, you can effectively communicate the importance and functionality of the
Definitions
object to your users, helping them understand the changes and how to interact with your Dagster project.
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