Im trying to set parameters in a revit family named “Tank Parameter Test”
Hi @gavin.hazlett ,
Could you share what dating is going through the nodes and what the error message is? Most of the times if you read the error message well you can easily spot what the issue is 
Here is the error message:
Warning: FamilyDocument.SetParameterValueByName operation failed.
Value cannot be null.
Parameter name: familyType
For the python script I created a script that creates a GUI that asks for input values for the parameters heres the code:
import clr
# import windows form
clr.AddReference("System.Windows.Forms")
# import system drawing
clr.AddReference("System.Drawing")
# import system
import System
from System.Windows.Forms import *
from System.Drawing import *
# Create a Class Form
def CreateMyForm():
form1 = Form()
form1.Text = "Tank Values" # Update the title here
label = Label()
label.Text = "Tank Diameter (in.):"
label.AutoSize = True
label.Location = Point(10, 10)
textbox = TextBox()
textbox.Location = Point(label.Right + 5, label.Top)
textbox.Size = Size(100, 20)
applyButton = Button()
applyButton.Text = "Apply"
applyButton.Location = Point(10, form1.ClientSize.Height - 10 - applyButton.Height)
applyButton.DialogResult = DialogResult.OK
applyButton.Click += lambda sender, event: form1.Close() # Close the form when Apply button is clicked
form1.AcceptButton = applyButton # Set the AcceptButton to be the Apply button
form1.Controls.Add(label)
form1.Controls.Add(textbox)
form1.Controls.Add(applyButton)
form1.Size = Size(300, 300)
form1.ShowDialog()
if form1.DialogResult == DialogResult.OK:
enteredValue = textbox.Text
return enteredValue # Return the value entered in the text box
return None
if IN[0]:
enteredValue = CreateMyForm()
OUT = enteredValue
It seems like either the FamilyType you supplied doesn’t exist or the value you are supplying through the Python Script is null.
If that is not the case for both show what data is going through each node
The value seems to be null even though it is stored in the python script block for some reason also I am not sure what is meant by family type… i just supplied a string with the name of the revit family
Share the dyn file please
Hola Amigo @gavin.hazlett buenas. This is very Confusing, but nodes in revit are very “Veddetes” When it comes to names, values and data types of Parameters and Families, you have to be very careful when supplying the information! I hope this helps you!!
Thank you! it works
