Skip to main content

DB_Column.map

mapfunctionskip_nothingexpected_value_type

Aliases: transform column

Documentation​

Applies function to each item in this column and returns the column of results.

Arguments​

  • function: The function to apply to each element of self column.
  • skip_nothing: If True, Nothing values will be skipped. Otherwise, Nothing values will be passed to the function.
  • expected_value_type: The expected value type of the resulting column. If Auto, the value type will be inferred from the values returned by function.

Examples​

Multiply each element of the column by itself.​

      import Standard.Examples

      example_map = Examples.integer_column.map (x -> x * x)

Errors​

  • If any of the values returned by function do not fit the expected value type, an Invalid_Value_Type error is raised.
  • If the function raises a dataflow error on any row, the first such error is propagated.
  • If an invocation of the function returns a value with warnings, these warnings are attached to the overall result.