Getting MEL code to work in Python

Rigging
1

A new script I am working on in Python requires me to make one mesh wrap around another. This line of code in MEL does exactly that:

string $wrap_name[] = doWrapArgList "6" { "1","0","0.1", "2", "1", "0", "0" };

I need that to work but in Python. I have tried countless variations of the code, even using maya.mel.eval but I haven’t had any luck getting it to work. I’ve tried checking google but came up short there too. Any help would be awesome, even if it’s just a suggestion. :):

2

Make sure you are escaping the double quotes with backslashes correctly. I’m not sitting in front of Maya right now, so this is untested.

import maya.mel as mm
myPythonVariable = mm.eval(“doWrapArgList “6” { “1”,“0”,“0.1”, “2”, “1”, “0”, “0” };”)

Alternatively, you could wrap the string in single quotes:

import maya.mel as mm
myPythonVariable = mm.eval(‘doWrapArgList “6” { “1”,“0”,“0.1”, “2”, “1”, “0”, “0” };’)

3

Thank you so much man. Where’s a huge thumbs up smiley when you need one? :D:

One question though, whats the maya.mel? I use:

import maya.cmds
maya.mel.eval(“doWrapArgList “6” { “1”,“0”,“0.1”, “2”, “1”, “0”, “0” };”)

And that also works. So I am curious what the difference is between the two?

4

Python is really modular by nature, as such you can specify which parts of the code base you want to utilize. This is done via importing…

import maya.cmds
imports ALL the commands into the default namespace.
import maya.mel as mm
imports just the mel commands within python into the mm namespace.

That modularity with importing combined with namespaces makes your code shorter to write and more secure. Tons of commands in the default namespace can cause issues.

import maya.cmds as cmds - That’s the convention I picked up and use. This way I can use cmds.sphere(blah, foo) vs maya.cmds.sphere(blah, foo)

I’ve come to MEL and python from not a programming background, so someone please correct me if I’ve misspoken technically.

5

definitely makes it shorter to write. Not too sure what you mean by more secure…Can you elaborate on that?

6

I’m under the impression that maya.cmds certainly brings in all maya commands (for the most part, some of the string functions and junk are stripped because they’re useless), but maya.mel is only used to call the mel eval command.

so import maya.mel as mel

mel.eval(‘MyAwesomeStringCommand’)

that’s about it.

7

At school they taught us:

import maya.cmds as cmds

for any of our python coding.

8

[QUOTE=UncCheezy;7563]Not too sure what you mean by more secure…Can you elaborate on that?[/QUOTE]

Probably meaning that you can avoid an import that overwrites an existing name:

from maya.cmds import *

would create a reference to a select() in the global, which isn’t too bad initially until you do something like

from select import select

Now select() refers to the version imported from the select module vs

import maya.cmds as mc

which creates mc.select().

Definitely good to come up with a set of blessed namespaces for your studio/team, at 343i we allow:


import pymel.core as pm

#or
import pymel.all as pm

# pymel.all is discouraged for production, usually we only allow this for prototyping and as the result of conversion
# scripts should be scaled back to pymel.core if possible before final code review

Slightly off topic but related, probably doesn’t hurt to have a standard order for importing either. Ours goes something like (off the top of my head):


# standard lib
import os

# external lib
import scipy
import pymel.core as pm

# C#
import clr
import System.Collections.ObjectModel

# internal lib
import animation.maya.api
import character.export

# siblings
import api

# plugins, privates, constants, etc

Seems like alot, but when dealing with code from numerous sources, consistency is key. In a pinch, PEP-8 is your friend.

9

I’m so nit picky with my code, I have tried to go through someones code that doesn’t care what it looks like, and it’s a nightmare. I just wish I was as quick with MEL as I am with Python. Otherwise I could avoid running into problems where Python has no idea what I am trying to do cause it’s a MEL only command. :laugh: