How to use dictionary yielded from other solid in a composite Solid?

Question

For example I have a solid named initiate_load , it is yielding a dictionary and an integer , something like :

@solid(
    output_defs=[
        OutputDefinition(name='l_dict', is_required=False),
        OutputDefinition(name='l_int', is_required=False)
    ],
)
def initiate_load(context):
    .... 
    ....

    yield Output(l_dict, output_name='l_dict')
    yield Output(l_int, output_name='l_int')

I have a composite_solid also ,let's say call_other_solid_composite

and I am passing l_dict and l_int to this composite_solid and I am using the l_dict to get the values mapped to its keys. Something like.

@composite_solid
def call_other_solid_composite(p_dict,p_int):
    l_val1 = p_dict['val1']
    ...
    ...

Then I am getting a Error as :TypeError: 'InputMappingNode' object is not subscriptable. I searched everywhere but can't find a solution . The documentation is also of no help . I have use case that I need to parse those values . Any help will be appreciated.

Answer 1

Similar to methods decorated with @pipeline, you should not think of methods decorated with @composite_solid as regular python methods. Dagster will wrap them and make it something completely different. That's why the p_dict parameter cannot be used inside the method as a regular method parameter.

To achieve what you want, you have a couple of options:

• pass the p_dict parameter directly in another solid and inside this solid you will be able to do l_val1 = p_dict['val1']
• next to the yields you now have in the initiate_load method, you can yield p_dict['val1'] as an output as well. This allows you to use both the dict and the 'val1' value as inputs in other solids (also in your composite)
• you can have a solid in your composite solid that yields the p_dict['val1'], this allows you to use this value as an input for other solids inside the composite.

Hope this helps. For reference, the documentation about the composite solids can be found here.

A small remark on the snippets you provided. Dagster has a very neat typing system, it is best practice to use this as much as possible.