user: What is Select Similar and how is it used in Blender Python scripting?

assistant: # Select Similar

Select geometry that has similar certain properties to the ones selected,
based on a threshold that can be set in tool properties after activating the tool.
Tool options change depending on the selection mode:

Vertex Selection Mode:
:   Normal
    :   Selects all vertices that have normals pointing in similar directions to those currently selected.

    Amount of Adjacent Faces
    :   Selects all vertices that have the same number of faces connected to them.

    Vertex Groups
    :   Selects all vertices in the same [vertex group](../properties/vertex_groups/index.xhtml).

    Amount of Connecting Edges
    :   Selects all vertices that have the same number of edges connected to them.

Edge Selection Mode:
:   Length
    :   Selects all edges that have a similar length as those already selected.

    Direction
    :   Selects all edges that have a similar direction (angle) as those already selected.

    Amount of Faces Around an Edge
    :   Selects all edges that belong to the same number of faces.

    Face Angles
    :   Selects all edges that are between two faces forming a similar angle, as with those already selected.

    Crease
    :   Selects all edges that have a similar [Crease](../editing/mesh/transform/basic.xhtml#modeling-edges-crease-subdivision)
        value as those already selected.

    Bevel
    :   Selects all edges that have the same *Bevel Weight* as those already selected.

    Seam
    :   Selects all edges that have the same *Seam* state as those already selected.
        *Seam* is a mark used in [UV texturing](../../../editors/uv/index.xhtml#editors-uv-index).

    Sharpness
    :   Selects all edges that have the same *Sharp* state as those already selected.
        *Sharp* is a mark used by the [Edge Split Modifier](../../modifiers/generate/edge_split.xhtml).

Face Selection Mode:
:   Material
    :   Selects all faces that use the same material as those already selected.

    Area
    :   Selects all faces that have a similar area as those already selected.

    Polygon Sides
    :   Selects all faces that have the same number of edges.

    Perimeter
    :   Selects all faces that have a similar perimeter (added values of its edge lengths).

    Normal
    :   Selects all faces that have a similar normal as those selected.
        This is a way to select faces that have the same orientation (angle).

    Co-planar
    :   Selects all faces that are (nearly) in the same plane as those selected.

    Flat/Smooth
    :   Selects all faces with similar [face shading](../editing/face/shading.xhtml).

    Freestyle Face Marks
    :   Selects all faces with similar [Freestyle Face Marks](../editing/face/face_data.xhtml#bpy-ops-mesh-mark-freestyle-face).

Compare
:   For quantitative properties, this property selects the type of comparison to between the two numerical values.

    Equal:
    :   Select items with the same value as the active item’s chosen property.

    Greater:
    :   Select items with a larger value as the active item’s chosen property.

    Less:
    :   Select items with a smaller value as the active item’s chosen property.

Threshold
:   For quantitative properties, this property controls how
    close the property’s values have to be in the comparison.