insert

append only knows one place to put things: the end. insert is the node for when "the end" isn't good enough - it drops an item at any position you specify, shoving the rest of the list down to make room. It's the fine-grained list editor of the Data List family.

It's part of Basic data handling, StableLlama's zero-dependency utility pack.

How it works

Python's list.insert(index, item), on a copy of the input list (it returns a new list rather than mutating, so it chains cleanly in a graph). Give it a list, an index, and an item, and the item lands at that position with everything after it shifted right. A few indexing notes that behave just like Python:

• Insert at 0 to prepend - item becomes the new head.
• Insert at the list's length to effectively append.
• Inserting past the end just appends; negative indices count from the end.

The output list is a data list, so the modified collection keeps flowing as a batch.

The inputs and output

• list (*) - the list to modify.
• index (INT, default 0) - where the item goes.
• item (*) - the value to insert.
• list (output) - the new list with the item in place.

A realistic use

Order matters when position encodes meaning - say a list of style tags where the first entry controls the dominant look, or a sequence of prompts meant to run in order. Insert lets you prepend a global instruction before a computed batch, or splice a value into the middle of a list you've assembled incrementally.

Installing it

ComfyUI Manager → search "Basic data handling", or:

cd ComfyUI/custom_nodes
git clone https://github.com/StableLlama/ComfyUI-basic_data_handling

Restart. No dependencies, no models.

Common issues

• "The item went to the end and I wanted the middle." Check your index - inserting at a value larger than the list length appends. And remember indexing starts at zero.
• "I wanted it at the front." Insert at index 0. It's the same node, just set the position.
• "This didn't mutate my original list." Correct - the node returns a new list. If you're seeing the old list downstream, you wired the output from the wrong place; the original input list is untouched by design.
• "I'm really just adding to the end." Then append or extend is simpler and says what you mean. Insert earns its keep only when the position actually matters.