# Python based Extension Development API: ColumnParameter for input\_table\_group

**URL:** <https://forum.knime.com/t/python-based-extension-development-api-columnparameter-for-input-table-group/91918>\
**Category:** Node Development\
**Created:** [May 11, 2026, 6:11pm UTC](https://forum.knime.com/t/python-based-extension-development-api-columnparameter-for-input-table-group/91918 "2026-05-11T18:11:44Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![joh\_elf](https://forum-cdn.knime.com/letter_avatar_proxy/v4/letter/j/ed655f/32.png) [@joh\_elf](https://forum.knime.com/u/joh_elf)\
**Post date:** [May 11, 2026, 6:11pm UTC](https://forum.knime.com/t/python-based-extension-development-api-columnparameter-for-input-table-group/91918/1 "2026-05-11T18:11:45Z")

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Hi all,

I’m using the Python Extension Development API. I want to set up a node with `input_table_group` to support an **arbitrary number of input tables** together with a `ColumnParameter` `ParameterArray` **to select one column from each input table.**

It seems like this is not yet implemented. Or is there any way to do this?

My current MWE where I tried to implement this:

```python
@knext.parameter_group(label="Column Selection")
class ColSelections:
    colsel: knext.ColumnParameter = knext.ColumnParameter(
        label="Cols",
        description="Select cols",
        default_value=None,
    )

@knext.node(
    name="Cf Node",
    node_type=knext.NodeType.MANIPULATOR,
    icon_path="icons/daly_elephant_small-64-64.png",
    category=mtu_base_category,
)
@knext.input_table_group(
    name="Tables to Concatenate",
    description="Tables to concatenate to base table",
)
@knext.output_table(
    name="Output Table", description="Something"
)
class CfNode:
    """Do something."""

    col_selection: knext.ParameterArray = knext.ParameterArray(
        label="Column Selections",
        description="Select the columns.",
        parameters=ColSelections(),
        array_title="Selections",
    )

    def configure(
        self,
        configure_context: knext.ConfigurationContext,
        input_schemas: list[knext.Schema],
    ) -> knext.Schema:
        for pa, schema in zip(self.col_selection, input_schemas):
            pa.colsel.apply(schema)

        return input_schemas[0]

    def execute(
        self,
        exec_context: knext.ExecutionContext,
        input_tables: list[knext.Table],
    ) -> knext.Table:
        return input_tables[0]

```

I also tried implementing this in many different ways, but it seems like Knime does not yet support this?

Any help is appreciated.

Thanks in advance and best regards,

Johannes

---

<div class="post-metadata">

**Author:** ![joh\_elf](https://forum-cdn.knime.com/letter_avatar_proxy/v4/letter/j/ed655f/32.png) [@joh\_elf](https://forum.knime.com/u/joh_elf)\
**Post date:** [May 18, 2026, 6:17pm UTC](https://forum.knime.com/t/python-based-extension-development-api-columnparameter-for-input-table-group/91918/2 "2026-05-18T18:17:50Z")

</div>

Hi @carstenhaubold or @ScottF,

any feedback from your side?

Thanks in advance and best regards,

Johannes

---

<div class="post-metadata">

**Author:** ![system](https://forum-cdn.knime.com/uploads/default/original/1X/ab3ccf34482a0329361734a18199390177204f15.png) [@system](https://forum.knime.com/u/system)\
**Post date:** [August 16, 2026, 6:17pm UTC](https://forum.knime.com/t/python-based-extension-development-api-columnparameter-for-input-table-group/91918/3 "2026-08-16T18:17:58Z")

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