[Maya-Pymel] parent to world comand results in error if object is already in world.

[Red]

Hello all,

If I try to unparent an object but the object is already part of the
world then the following command results in an error:

>> parent(anyObject, world = True)
# Error: Maya command error
# Traceback (most recent call last):
# File "<maya console>", line 1, in <module>
# File "C:\Program Files\Autodesk\Maya2011\Python\lib\site-packages
\pymel\internal\pmcmds.py", line 98, in wrappedCmd
# res = new_cmd(*new_args, **new_kwargs)
# RuntimeError: Maya command error #

However if I do the same from within maya with the unparent 'buton'
only get a warning message saying:

# Warning: line 0: Object, 'myObject', skipped. It is already a child
of the parent, 'world'. #

Is this just a bug within pymel ?
Or am I missing something here?

Greets
Red

[Paul Molodowitch]

Well, first of all, comparing gui 'buttons' are not a direct / fair comparison to pymel commands, since they are almost always calling a mel script, which does some other stuff as well.

For instance, in this case, it calls the 'Unparent' runtime command, which in turn calls scripts/others/performUnparent.mel

A better comparison would be the maya.cmds.parent - which also throws an error in this situation:

import maya.cmds

cube = maya.cmds.polyCube()[0]

maya.cmds.parent(cube, world = True)

# Warning: Object, 'pCube1', skipped. It is already a child of the parent, 'world'. #

# Error: Maya command error

# Traceback (most recent call last):

# File "<maya console>", line 3, in <module>

# RuntimeError: Maya command error #

However... having said that, I also tried the mel command (since it seemed odd that it would throw a warning AND an error), and that did NOT error - it only gave the warning.  So my guess is that there's an error in Autodesk's implementation of the python maya.cmds.parent cmd, which pymel relies on.

Of course, it would be possible to make pymel behave like the mel command, and not throw an error in this situation.  However, I'm not sure it's clear in which manner it SHOULD behave in this case (ie, should it emulate the behavior of the python or mel command?)... so I'd lean towards leaving it the way it is, since that won't break anyone's existing code...

- Paul

--
http://groups.google.com/group/python_inside_maya

[Jan:]

Tank you for the explanation.

Yes I do agree to leave it like it is. But it striked me as odd.
A simple 'If parent is not none' check solved the problem.

Thank you again for the explanation. I'm starting to understand more and more of the inner workings of pymel :)

2010/8/25 Paul Molodowitch <elro...@gmail.com>

--
http://groups.google.com/group/python_inside_maya