How to Select Elements with Revit API

There are plenty of reasons why we need to select elements for our scripts. So Let's learn how to do it!

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M3-01

How to Select Elements with Revit API

There are plenty of reasons why we need to select elements for our scripts. So Let's learn how to do it!

Resources

Revit API Docs: Selection

PEP8: Python Type Hinting

Summary

Selection Class

To control selection in Revit with python we need to use Selection Class.

It has plenty of helpful methods. So let's go through most used ones for selection and understand how to use them.

Methods:
GetElementIds
PickElementsByRectangle
PickObject
PickObjects
SetElementIds
PickBox
PickPoint

Get Selection Instance

To use any of these methods we need to get an instance of Selection Class.
Luckily, there is a property .Selection in our uidoc instance. So it's very simple to get it

💡We can also specify type of a variable so pyCharm can give us better autosuggestions by using '#type: …' syntax.

from Autodesk.Revit.UI.Selection import Selection

uidoc     = __revit__.ActiveUIDocument
selection = uidoc.Selection #type: Selection

👆 We will need that for all the snippet below!

GetElementIds Method

This method will return list of ElementId of your current selection in Revit UI. I love using it, as it can be a very quick approach to select elements.

#🔷 Get Selected Elements
selected_elements = selection.GetElementIds()

for e_id in selected_elements:
    print(e_id)

    # Convert ElementId to Element
    e = doc.GetElement(e_id)
    print(e, e.Category.Name)

    # Filter Selection
    if type(e) not in [Wall, Floor]:
        print('Wrong Element: {}'.format(e))
    else:
        print('Wall/Floor: {}'.format(e))

Since this method returns us ElementIds, don't forget to turn them into actual elements, so we can read their properties and methods.

💡Optionally, we can also introduce very basic filter by checking type of elements.

PickElementsByRectangle Method

This method is great, because it's a single line of code, and it already returns you list of Elements instead of ElementIds.

#🔷 PickElemnetsbyRectangle
selected_elements = selection.PickElementsByRectangle('Title Here')
print(selected_elements)

But unfortunately, there is no confirmation needed on your selection. So if you selected wrong elements, you would need to run your tool again to correct it. And if you want to fix that, PickObjects is going to solve that issue for you.

PickObject Method

This is great for selecting a single element.

But be aware that it returns a Reference. Luckily, we can use the same doc.GetElement() method and provide reference instead of an ElementId.

#🔷 PickObject
from Autodesk.Revit.UI.Selection import ObjectType

ref_picked_object = selection.PickObject(ObjectType.Element)
picked_object     = doc.GetElement(ref_picked_object)

print(picked_object)

💡 We can also create a for/while loop and ask user to select single element over and over and do something with it. For example we could change color overrides of each element one by one by clicking on them.

PickObjects Method

This method is similar to single PickObject. But this time we would need a list comprehension to convert all references to actual elements.

#🔷 PickObjects
from Autodesk.Revit.UI.Selection import ObjectType

ref_picked_objects = selection.PickObjects(ObjectType.Element)
picked_objects     = [doc.GetElement(ref) for ref in ref_picked_objects]

for el in picked_objects:
    print(el)

SetElementIds Method

We use this method whenever we want to change selection in Revit UI.

It takes a single argument - ICollection[ElementId] that includes new selection.

#🔷 SetElementIds (P.S. modify ElementId to yours!)

# Prepare List[ElementId] - A
python_list = [ElementId(347164),
               ElementId(347244),
               ElementId(347326),
               ElementId(347399)]
new_selection = List[ElementId](python_list)

# Prepare List[ElementId] - B
new_selection = List[ElementId]()
new_selection.Add(ElementId(347164))
new_selection.Add(ElementId(347244))
new_selection.Add(ElementId(347326))
new_selection.Add(ElementId(347399))

#🎯 Set New Selection
selection.SetElementIds(new_selection)

PickPoint Method

We can also ask user for a location input such as Point. This might be great for many tools.

#🔷 PickPoint
picked_pt = selection.PickPoint()
print(picked_pt)
print(type(picked_pt)) #XYZ type

💡 Points are represented with XYZ class in Revit API. Also pay attention as it uses feet for X,Y,Z coordinates in Internal Coordinate System.

PickBox Method

Alternatively, we can ask user to Pick a Box. PickedBox has properties to get 2 points:

.Min - Bottom Left
.Max - Top Right

#🔷 PickBox
from Autodesk.Revit.UI.Selection import PickBoxStyle

pb_style = PickBoxStyle.Directional
picked_box = selection.PickBox(pb_style, 'Message')
print(picked_box.Min)
print(picked_box.Max)

HomeWork

👉 Now you have all the main snippets for selecting elements with Revit API. Now it's your turn to practice

✅ Try to select elements with snippets and print results.
✅ Place Snippets that you are going to reuse in lib

⌨️ Happy Coding!

Complete Lesson

Questions:

Which Selection method should I use?

Discuss the lesson:

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