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Parameter with Python list

The value of the PythonPart parameter can be created as a Python list object of the used value type.

One-dimensional list

Single dimensional list

<Parameter>
    <Name>CubeDimensions</Name>
    <Text> </Text>
    <Value>[1000.,1200.,1400.,1600.,1800.]</Value><!--(1)!-->
    <ValueType>Length</ValueType>
</Parameter>

  1. Any Python statement, which creates a list, can be used here:

    • []
    • [1000.] * 5
    • [[0 for x in range(3)] for y in range(5)]

Info

When a list consists of simple objects, like Integer, String, etc., use the coma , as separator. However, when a list consist of complex objects, that includes strings/integers/etc. e.g., a list of tuples or points use the semicolon ; as separator:

<Parameter>
    <Name>PointList</Name>
    <Text></Text>
    <Value>[Point2D(0,500);Point2D(0,0);Point2D(400,20)]</Value>
    <ValueType>Point2D</ValueType>
</Parameter>

Two-dimensional list

Two dimensional list

<Parameter>d
    <Name>Coordinates</Name>
    <Text>Coordinate</Text>
    <Value>[[0 for x in range(3)] for y in range(5)]</Value>
    <ValueType>Length</ValueType>
</Parameter>

Empty list

To initialize an empty list, use the square brackets with an underline [_], like this:

<Parameter>
    <Name>PointList</Name>
    <Text></Text>
    <Value>[_]</Value><!--(1)!-->
    <ValueType>Point2D</ValueType>
</Parameter>

  1. Initializing an empty list like this is important, when the list elements are objects like point or common properties. Initializing the list with [] would result in a list containing one (empty) object, e.g. [Point2D(0,0,0)].

    In case of python built-in objects like string or integer, it will make no difference.

To initialize a list containing a certain amount of empty elements, like common properties or lines we can use the square brackets with an appropriate number of semicolons in it, like this:

<Parameter>
    <Name>PointList</Name>
    <Text></Text>
    <Value>[;;]</Value><!--(1)!-->
    <ValueType>Point2D</ValueType>
</Parameter>

  1. This will result in a python list consisting of 3 zero points

    [Point2D(0, 0), Point2D(0, 0), Point2D(0, 0)]

Optional tags

Dimensions

If the length of the list is supposed to be dynamic, the tag <Dimensions> must be added to the parameter definition.

<Parameter>
    <Name>CubeDimensions</Name>
    <Text> </Text>
    <Value>[1000.,1200.,1400.,1600.,1800.]</Value>
    <ValueType>Length</ValueType>
    <Dimensions>CubeCount</Dimensions><!--(1)!-->
</Parameter>

  1. The tag can contain:

    • an integer constant <Dimensions>3</Dimensions>,
    • a name of an existing Integer parameter <Dimensions>CubeCount</Dimensions>,
    • a formula created by parameter names <Dimensions>CubeCount + 1</Dimensions>.
<Parameter>
    <Name>Coordinates</Name>
    <Text>Coordinate</Text>
    <Value>[[0 for x in range(3)] for y in range(5)]</Value>
    <ValueType>Length</ValueType>
    <Dimensions>CubeCount,CoordDimension3D + 2</Dimensions><!--(1)!-->
</Parameter>
  1. In this case two values separated with , must be provided

Initial row index

Each row of the list in the property palette is tagged with a row index. By default, the indexing starts at 0, but this can be changed by adding the tag <ValueListStartRow>.

<Parameter>
    <Name>Coordinates</Name>
    <Text>Coordinate</Text>
    <Value>[[0 for x in range(3)] for y in range(5)]</Value>
    <ValueType>Length</ValueType>
    <ValueListStartRow>-1<!--(1)!--></ValueListStartRow>
</Parameter>

  1. Setting the value to -1 will result in hiding the index completely. The result will look like this:

    Two dimensional list with no index

Show specific row

If only one row of the list is to be displayed in the property palette, it can be achieved with the tag <ValueIndexName>.

<Parameter>
    <Name>Coordinates</Name>
    <Text>Coordinate</Text>
    <Value>[[0 for x in range(3)] for y in range(5)]</Value>
    <ValueType>Length</ValueType>
    <ValueIndexName>VisibleRowIndex</ValueIndexName><!--(1)!-->
</Parameter>
  1. The value must be a name of an existing Integer or_IntegerComboBox_ parameter. The row index starts from 1.

Accessing list item index

The special keyword $list_row allows access to the current list item index. The index starts with 0.

<Parameter>
    <Name>EnableVisibleItemsByListRow</Name>
    <Text></Text>
    <Value>[1000.,1200.,1400.,1600.,1800.,2000]</Value>
    <ValueType>Length</ValueType>
    <MinValue>100</MinValue>
    <Visible>$list_row != HideRowListRow</Visible>
    <Enable>$list_row != EnableRowListRow</Enable>
</Parameter>

Grouping

Individual parameter with value lists can be grouped to combine the controls with the same list item index into a block. This can be done by putting the list parameters into a ListGroup parameter. Here are short examples of how to group list parameters...

Group one dimensional list

<Parameter>
    <Name>ListGroup1</Name>
    <ValueType>ListGroup</ValueType>

    <Parameter>
        <Name>GroupExpander</Name>
        <Text>"Field " + str($list_row + 1)</Text>
        <ValueType>Expander</ValueType>

        <Parameter>
            <Name>SectionName</Name>
            <Text>Section name</Text>
            <Value>["A", "B", "C"]</Value>
            <ValueType>String</ValueType>
        </Parameter>

        <Parameter>
            <Name>Distance</Name>
            <Text>Distance</Text>
            <Value>[1000, 2000, 3000]</Value>
            <ValueType>Length</ValueType>
        </Parameter>

        <Parameter>
            <Name>GroupButtonRow</Name>
            <Text>"Group " + str($list_row + 1)</Text>
            <ValueType>Row</ValueType>
            <Parameter>
                <Name>GroupButton</Name>
                <Text>Edit</Text>
                <EventId>1000</EventId>
                <ValueType>Button</ValueType> <!--(1)!-->
            </Parameter>
        </Parameter>
    </Parameter>
</Parameter>

  1. When a button is added to the group, the final event ID is a combination of the <EventId> and the row index. The extraction of these values is done with bitwise shifting of the event_id value as follows:

    block_row_index = event_id >> 16
block_event_id  = event_id - (block_row_index << 16)

Group one dimensional list with row

<Parameter>
    <Name>ListGroup</Name>
    <ValueType>ListGroup</ValueType>

    <Parameter>
        <Name>GroupRow</Name>
        <Text>"Field " + str($list_row + 1)</Text>
        <ValueType>Row</ValueType>

        <Parameter>
            <Name>SectionName</Name>
            <Text>Section name</Text>
            <Value>["A", "B", "C"]</Value>
            <ValueType>String</ValueType>
        </Parameter>

        <Parameter>
            <Name>Distance</Name>
            <Text>Distance</Text>
            <Value>[1000, 2000, 3000]</Value>
            <ValueType>Length</ValueType>
        </Parameter>

        <Parameter>
            <Name>GroupButtonRow</Name>
            <Text>"Group " + str($list_row + 1)</Text>
            <ValueType>Row</ValueType>
            <Parameter>
                <Name>GroupButton</Name>
                <Text>Edit</Text>
                <EventId>1000</EventId>
                <ValueType>Button</ValueType>
            </Parameter>
        </Parameter>
    </Parameter>
</Parameter>

Example

The example implementation of the list value type can be found here:

  • …\etc\Examples\PythonParts\PaletteExamples\ValueList.pyp
  • …\etc\PythonPartsExampleScripts\PaletteExamples\ValueList.py