View Full Version : Python in Mel Expressions?

09 September 2010, 11:40 AM
Hi Everybody,

I am pretty new to scripting, so I hope I can explain everything so it makes sence.

I've been working on a python plugin that requires for a mel expression to be created. The only problem is that I don't know how to add python lists to the expression editor.

Basic Idea of the problem:
selectedObjects =, transforms=True)
cmds.expression( name=controlObject+"_Exp", string="$List[] = {selectedObjects};" )

This gives an error.
This is what it should look like after the script is ran.

Lets say the selectedObjects = ["Head", "Root", "World"]
The end result in the expression editor should be:
$List[] = {"Head", "Root", "World"};

How do I do something like that?

09 September 2010, 01:54 PM
I think first problem is that you don't add objects , you add string selectedObjects.
It should look something like this.
cmds.expression( name=controlObject+"_Exp", string="$List[] = {"+selectedObjects[0]+"};")
Or if it is " dinamic" selection you made for loop:
for i in selectedObjects:

Second problem you need to declare variable List(this is mel btw :) ):

string $List[] = {"Head", "Root", "World"};

09 September 2010, 11:08 PM
Thank you for your reply, but it didn;t solve the problem.

The problem remains that because the complete expression is between "", the python lists are being processed as text and not as a python list.

Does anybody have an idea how to fix that?

09 September 2010, 12:10 AM
I hope this solve your problem:

import maya.cmds as mc
def test1():
for i in list:
exp="string $list[]={"+melList[0:-1] + "};"

09 September 2010, 10:28 AM
That worked. Thank you very much.

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09 September 2010, 10:28 AM
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