calculate.expr produces one named column

What calculate.expr is

calculate.expr is the formula used to produce one named output column from the current frame.

It does not filter rows and it cannot declare several outputs at once. Use separate calculate steps or a script with an explicit output mapping.

What it contains

• Current column references — Names available when the step begins.
• Arithmetic expression — Evaluated by pandas eval with the Python engine.
• One destination column — Declared separately by calculate.column.

Name the output outside the formula

Separating column from expr makes assignment explicit. A reader can identify what changes without parsing the expression text.

Run the complete example

Copy this manifest from the verified documentation project, then run it from the repository root.

version: "1.0"
transformations:
  steps:
    - cast:
        mapping: {amount: float}
    - calculate:
        column: amount_with_tax
        expr: "amount * 1.2"

hdrctl run examples/tutorial/dsl-elements -t compute.yaml

  ✅ Pipeline completed successfully in 2.9s
  Rows read   : 30
  Rows written: 30

The relevant command syntax, copied from hdrctl run --help:

hdrctl run [PATH]
  -s, --sources FILE          explicit path to sources.yaml
  -d, --destinations FILE     explicit path to destinations.yaml
  -t, --transformations FILE  explicit path to transformations.yaml
  -P, --param KEY=VALUE       override a parameter, repeatable

Close by

• Compute — calculate and script
• filter.expr — boolean predicates
• script.code — multiple outputs
• Columns — prepare types
• Reference — calculate keys