Hey, Did You Know: Lacing Operations

Lists-Logic
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Hey, did you know how Lacing Operations work in Dynamo? :thinking: It is important to understand how to manage data flow between lists! :star2: Lacing determines how nodes handle list combinations in your scripts. :jigsaw: Here’s the quick breakdown:

:small_blue_diamond: Shortest: Matches lists element by element, stopping at the shortest list.
:small_blue_diamond: Longest: Extends the shorter lists by repeating their last elements to match the longest one.
:small_blue_diamond: Cross-Product: Generates every possible combination between elements of both lists.
:small_blue_diamond: Auto: Automatically adjusts the lacing mode based on the input lists and node logic.

Mastering lacing operations and list management in Dynamo will bring a lot of flexibility for your Dynamo workflows! :rocket:

Which lacing mode do you use the most? Or are you curious to explore a specific one? Let’s chat in the comments! :point_down:

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I’m not sure if it’s okay to reply in this thread as I don’t see any other responses – but I’ll give it a try:
I have a question about the ‘auto’ lacing type – is it capable of producing a result that cannot be replicated by ‘shortest,’ ‘longest,’ or ‘cross-product’? I feel like I encountered something like this in a certain combination before, but I can’t figure out how to reproduce that behavior. Most of the time, ‘auto’ behaves like ‘shortest’ for me. Thanks for your help!

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Not really, but kinda. But it certainly makes life easier so you don’t want to remove it.

Auto lacing defaults to shortest lacing, except for when one input is a single input.

So if you have a list of letters such as [A, B] and a list of numbers such as [1, 2, 3, 4] wired into a + node with shortest lacing you get [A1, B2], but longest lacing you get [A1, B2, B3, B4], and cross product would be [ [A1, A2, A3, A4], [B1, B2, B3, B4] ]. So with Auto lacing in this situation both inputs are a list which means the lacing used is shortest, so we get [A1, B2]. But if you change the first input to just A auto lacing sees the single input and switches to longest lacing so you get [A1, A2, A3, A4].

Things get more complex as you add inputs (i.e. with setting multiple parameter values for a multiple elements to multiple sets of unique values), but this basically covers it. If you would like to see a more visual example, the Dynamo Office Hours series from WAY back when here covers it well.

The following session is also likely of interest, as it covers list levels.

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