Hi All is there a way to create dependencies between nodes w Hamilton Open Source #hamilton-help

Hi All, is there a way to create dependencies betw...

Joao Castro

02/05/2025, 1:44 PM

Hi All, is there a way to create dependencies between nodes when one of them returns None? For example, having a node creating a table in a db and then run another node after that. They way i thought was to return a boolean but wondering if there's another way recommended as I couldnt find anything in the docs. Thanks

Elijah Ben Izzy

02/05/2025, 5:57 PM

So there’s no special case but

None

and

NoneType

should work

Elijah Ben Izzy

02/05/2025, 5:58 PM

(3.10 or greater): https://docs.python.org/3/library/types.html#types.NoneType

Elijah Ben Izzy

02/05/2025, 5:59 PM

That said, there might be room for side-effects encoded in the library. Idea:

Copy code

h_types.SideEffect("Table_foo")

or something like that

👍 1

Stefan Krawczyk

02/05/2025, 6:00 PM

Copy code

def a(input: SomeType) -> None:
    # do stuff
    

def b(a: None, other_param: ...) -> some_other_type:
    return ...

Stefan Krawczyk

02/05/2025, 6:00 PM

@Joao Castro the above should work ^ ; i.e.

has None, and anything that depends on it just uses

None

as the type if you want it in the graph. Otherwise you could do a boolean, return metadata, etc. Up to you - that should still work.

👍 1

Stefan Krawczyk

02/05/2025, 6:13 PM

@Joao Castro if that gets ugly, we could also consider a decorator that declares this, but I like the explicitness here.

👍 1

Joao Castro

02/06/2025, 9:29 AM

Thanks guys!

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