Accumulate¶
Builds up an ordered list of values across steps or iterations. Each call appends the provided value to an accumulation container, gracefully handling first-time initialization and no-op behavior when the value to add is None.
Usage¶
Use this node when you need to collect multiple values over time into a single list, such as aggregating results from a loop or conditional branch. Feed the 'accumulation' output back into the next call's 'accumulation' input to keep appending values, and supply the new item via 'to_add'.
Inputs¶
| Field | Required | Type | Description | Example |
|---|---|---|---|---|
| to_add | True | WILDCARD | The next item to append to the accumulation. Accepts any type. If this is None, the node will not add anything and will forward the existing accumulation. | 42 |
| accumulation | False | ACCUMULATION | The current accumulation container. If omitted or None, a new accumulation is started. Can be either a proper ACCUMULATION object or a raw value (which will be normalized). | {"accum": ["a", "b"]} |
Outputs¶
| Field | Type | Description | Example |
|---|---|---|---|
| accumulation | ACCUMULATION | The updated accumulation container with the newly added item (if provided). Internally represented as an object with an 'accum' list. | {"accum": ["a", "b", "c"]} |
Important Notes¶
- Skips None values: If 'to_add' is None, the output simply forwards the existing accumulation (or creates an empty one if none exists).
- Initialization behavior: If no prior accumulation is provided, the node starts a new one containing only 'to_add' (unless 'to_add' is None, in which case it starts empty).
- Flexible input: If 'accumulation' is a proper ACCUMULATION (with an 'accum' list), the item is appended. If a raw value is provided as 'accumulation', it is normalized and the output becomes [accumulation, to_add].
- Order preserving: Items are appended in the order the node is executed.
- Type-agnostic: The accumulator can mix different value types in one list.
- Error handling: On internal errors, the node returns an empty accumulation {"accum": []}.
Troubleshooting¶
- Items are not appearing in the list: Ensure 'to_add' is not None for the steps where you expect an item to be appended.
- Accumulation resets unexpectedly: Verify you are reconnecting the previous 'accumulation' output back into the next node's 'accumulation' input each iteration.
- Unexpected first elements: If you pass a non-ACCUMULATION value into 'accumulation', the node will treat it as the first element and append 'to_add'. Use a proper ACCUMULATION or the previous output to avoid this.
- Empty result: If you see {"accum": []}, you may have started with None and 'to_add' was None, or an error occurred upstream. Provide a valid 'to_add' or confirm prior steps.
- Mixed types issues downstream: Downstream nodes must handle mixed types if you accumulate heterogeneous items. Filter or standardize types before accumulation if needed.