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Constant

You have values that don't change per quote - expense loadings, tax rates, minimum premiums. The Constant node stores them in one place so every part of your pipeline can reference them.

When to use

Use this to store values that don't change per quote - expense loadings, tax rates, minimum premiums, effective dates. These values are available to every downstream node.

A Constant has no inputs. Its output is a single-row table with one column per value. The panel has two tabs: CONFIG and COLUMNS.

The CONFIG tab

VALUES lists the constants, one row each:

Field What it does
Name (placeholder "name") The column the value becomes. A row without a name is left out of the output.
Value (placeholder "value") The value. A value that reads as a number becomes a decimal number (250 becomes 250.0); anything else stays text.
  • Add value adds a row, named constant_2, constant_3 and so on, with the value 0.
  • The bin at the end of a row (its tooltip reads "Remove") deletes it.

A new node starts with one value, constant_1 = 1.0. With no named values at all, the node outputs a single column called constant.

The COLUMNS tab

The COLUMNS tab chooses which of the constants the node passes on (see Working with any node).

Connecting to other nodes

The Constant node produces a single-row table. To give every row of your main data access to every constant, cross-join the two:

  • With an Edge Join: drag the Constant's output onto the connection that carries your data, then set JOIN TYPE to Cross.
  • In a Polars node: connect both, start from your data and add a Join another input step that joins the Constant's input with cross: every combination of rows. Then add steps that use the constants, such as an Add column step that multiplies base_premium by expense_loading.

Example

  1. Add a Constant node called params. Change the first row to expense_loading = 1.15.
  2. Click Add value twice and fill in tax_rate = 0.12 and min_premium = 250.
  3. Connect params and your data, quotes, to a Polars node. Start from quotes, add Join another input with cross: every combination of rows and params, then add Add column with Column name loaded_premium and the formula base_premium * expense_loading.

The Constant's preview is one row:

| expense_loading | tax_rate | min_premium |
|-----------------|----------|-------------|
| 1.15            | 0.12     | 250.0       |

and the Polars node's Generated code panel shows:

df = quotes
df = df.join(params, how="cross", suffix="_right")
df = df.with_columns(
    (pl.col("base_premium") * pl.col("expense_loading")).alias("loaded_premium")
)

Dates

Values are stored as text and turned into numbers where possible. For dates, type them as text (e.g. 2025-01-01) and convert them in a downstream Polars node if needed, for example with a Change types step to Date (date).

In the pipeline file

The node's settings are stored in a JSON sidecar, config/constant/<node name>.json, which the node's decorator in the pipeline's .py file names: @pipeline.constant(config="config/constant/<node name>.json").

Setting in the editor Stored as
VALUES values: a list of {"name": ..., "value": ...} pairs, with each value stored as text
COLUMNS tab selected_columns 
{
  "values": [
    { "name": "expense_loading", "value": "1.15" },
    { "name": "tax_rate", "value": "0.12" },
    { "name": "min_premium", "value": "250" }
  ]
}

See also:

  • Edge Join - to join the constants onto your data without a Polars node
  • Polars - for calculations that use the constants