Reverse List

ReverseList returns a new list with the elements of the input list in reverse order. First becomes last, last becomes first, nothing else changes - no sorting, no dedup, no surprises. It's the kind of node that sounds trivial until you need to flip the order of a batch and realize nobody ships one in core ComfyUI.

When you'd reach for it

Order matters more than people admit in ComfyUI. Reversed video frames, reversed latent batches for a "play it backwards" effect, reordered conditioning sequences, or simply correcting an upstream node that produced a list in the wrong order. The node is non-mutating - your input list is untouched - which makes it safe to drop into any pipeline.

How it works

The backend is list(reversed(py_list)) - a new list, reversed. The input is a wildcard *, and the class declares both INPUT_IS_LIST and OUTPUT_IS_LIST, so the engine treats the whole thing as a graph-level batch: an incoming list flows in, a reversed list flows out, each marked as a batch for downstream fan-out.

One detail worth knowing: if the input isn't actually a Python list, the node raises a ValueError ("Input must be a Python list"). It doesn't silently pass garbage through.

Inputs and outputs

• py_list (required, *) - the list to reverse.
• * (output, declared list) - the reversed list.

Installing it

Part of the comfy-ovum pack:

cd ComfyUI/custom_nodes
git clone https://github.com/sfinktah/comfy-ovum

Restart ComfyUI, or use ComfyUI Manager → search "comfy-ovum" → Install. No models, no GPU cost.

The deprecated tag

Here's the honest caveat: in the pack's source, ReverseList is marked DEPRECATED = True and registered as "ReverseListDEPRECATED(batch)". It's the old member of the reverse family, and the author split things into two maintained replacements:

• ReverseBatchOvum (ovum/lists/comfy) - the current batch variant, same list(reversed(...)) behavior, output declared as a graph list.
• ReverseListOvum (ovum/lists/python) - reverses a real Python list object, output as a single value.

This node still works and behaves like the batch variant, but it's the stepping stone. If you're building fresh, use ReverseBatchOvum for graph batches or ReverseListOvum for Python-list utilities - no reason to start new workflows on the deprecated one.