What is Dynamo?

Dynamo is an open-source visual programming environment that extends Autodesk Revit with algorithmic design and automation. You connect nodes on a canvas — each node performs one operation — to build scripts that automate repetitive tasks, generate geometry, extract data, and control Revit models without writing traditional code. Dynamo runs either inside Revit (Dynamo for Revit) or as a standalone sandbox application.

Node Types

• Input nodes — Number sliders, string inputs, boolean toggles, file path pickers. These are where data enters your graph.
• Action nodes — Perform operations: filter lists, query Revit elements, run math, call Revit API methods. The bulk of every script.
• Output nodes — Watch nodes show results; Transaction nodes write changes back to Revit (wrapped automatically by Element.SetParameterByName, etc.).

Python Script Node

• Insert via Add → Core → Scripting → Python Script
• Inputs arrive as IN[0], IN[1], …; your result goes into OUT
• Import Revit API: import clr; clr.AddReference('RevitAPI'); from Autodesk.Revit.DB import *
• Access the document with doc = DocumentManager.Instance.CurrentDBDocument
• Wrap writes in TransactionManager.Instance.EnsureInTransaction(doc) / ForceCloseTransaction()
• Use IronPython 2.7 syntax (CPython 3 available in Dynamo 2.13+ via CPython3 node)

Recommended Packages

Install via Dynamo → Packages → Search for Packages:

Recommended Workflow

• Start with Dynamo's built-in nodes — cover 80% of use cases without Python
• Use Element.GetParameterValueByName before writing a Python collector
• Always test on a non-production model or a linked copy
• Add Watch nodes at every stage to debug list levels (use @1 lacing for nested lists)
• Switch to Python only when built-in nodes can't access a Revit API class or you need loops with complex logic
• Save graphs as .dyn files in a shared folder — commit them to Git for version control

List Levels & Lacing

• Dynamo stores data in nested lists — understanding @L1, @L2 levels prevents mis-matched connections
• Shortest lacing: zip lists by shortest — safest default
• Longest lacing: repeats last item to fill — useful for single-value broadcasts
• Cross Product: all combinations — powerful but creates large lists
• Right-click a node input to set lacing; use List.Map and List.Flatten to manipulate structure