List to Accumulation | Deforum

Somewhere inside a Deforum loop you will run into the pack's own data type, the accumulation - a list that grows across loop iterations instead of existing all at once. List to Accumulation | Deforum is the converter that takes a normal list you already have and wraps it into that type so a loop can carry it. It's a bridge node: on one side the lists you build with Make List | Deforum, on the other the loop machinery that wants an accumulation.

The input is a single list (wildcard-typed, and marked as taking a list of values). The output is ACCUMULATION. Mechanically it's almost insultingly simple - the source wraps the list into the pack's {"accum": [...]} container - but that's the point: it exists so the type system lines up. ComfyUI's type checker is strict, and ACCUMULATION is a private type that only this pack's nodes speak. If you've produced a list of seeds, denoise values, or prompts and you want to hand it to a loop, this is the adapter.

Why does the pack bother with a separate type instead of just using lists? Because loops have a chicken-and-egg problem: a loop-carried value has to exist before the first iteration and be updated after every one, and a plain list is awkward for that. An accumulation is the pack's idiom for "a list being built incrementally by a loop." The companion family - Accumulate | Deforum (append), Accumulation Head / Accumulation Tail (pop), Accumulation Get Item, Accumulation Get Length, Accumulation to List - all read and write that container. In practice you'll usually start with one of those nodes building an accumulation from scratch, which is why this converter exists in the opposite direction: when your data already exists as a list (say, straight out of Integer List Generator | Deforum) and a loop wants it as an accumulation, convert rather than rebuild.

The honest caveat: outside this pack's loops, ACCUMULATION is meaningless to the rest of the ecosystem. If you convert a list and wire it into a core node, you'll get a type error - you must consume it with the pack's accumulation nodes. And since the input is wildcard-typed, the node trusts you to actually feed it a list; feed it a single value and you'll get a one-element accumulation that behaves, well, like a one-element list.

Installation is the pack: ComfyUI Manager → search "ComfyUI-Deforum" or deforum-comfy-nodes → install, restart. Manual: git clone https://github.com/deforum-art/deforum-comfy-nodes into ComfyUI/custom_nodes, then restart. No model downloads, no extra Python deps, and the repo relocated from XmYx/deforum-comfy-nodes to the deforum-art org, so old links may point at the original URL. It's a small node with a narrow job - but when your loop is complaining that it can't read the list you built, this is the adapter that unblocks the whole thing.