use external python script to open maya and run an

Question

Is it possible to call a script from the command prompt in windows (or bash in linux) to open Maya and then subsequently run a custom script (possibly changing each time its run) inside Maya? I am searching for something a bit more elegant than changing the userSetup file and then running Maya.

The goal here is to be able to open a .mb file, run a script to position the scene inside, setup a generic set of lights and then render the scene to a specific place and file type. I want to be able to set this up as a scheduled task to check for any new scene files in a directory and then open maya and go.

Thanks for the help!

Answer 1

A lot depends on what you need to do.

If you want to run a script that has access to Maya functionality, you can run a Maya standalone instance as in Kartik's answer. The mayapy binary installed in the same folder as your maya is the Maya python interpreter, you can run it directly the same way you'd run python.exe Mayapy has the same command flags as a regular python interpreter.

Inside a mayapy session, once you call standalone.initialize() you will have a running Maya session - with a few exceptions, it is as if you were running inside a script tab in a regular maya session.

To force Maya to run a particular script on startup, you can call the -c flag, just the way you would in python. For example, you can start up a maya and print out the contents of an empty scene like this (note: I'm assuming mayapy.exe is on your path. You can just CD to the maya bin directory too).

mayapy -c 'import maya.standalone; maya.standalone.initialize(); import maya.cmds as cmds; print cmds.ls()'
>>> [u'time1', u'sequenceManager1', u'renderPartition', u'renderGlobalsList1', u'defaultLightList1', u'defaultShaderList1', u'postProcessList1', u'defaultRenderUtilityList1', u'defaultRenderingList1', u'lightList1', u'defaultTextureList1', u'lambert1', u'particleCloud1', u'initialShadingGroup', u'initialParticleSE', u'initialMaterialInfo', u'shaderGlow1', u'dof1', u'defaultRenderGlobals', u'defaultRenderQuality', u'defaultResolution', u'defaultLightSet', u'defaultObjectSet', u'defaultViewColorManager', u'hardwareRenderGlobals', u'hardwareRenderingGlobals', u'characterPartition', u'defaultHardwareRenderGlobals', u'lightLinker1', u'persp', u'perspShape', u'top', u'topShape', u'front', u'frontShape', u'side', u'sideShape', u'hyperGraphInfo', u'hyperGraphLayout', u'globalCacheControl', u'brush1', u'strokeGlobals', u'ikSystem', u'layerManager', u'defaultLayer', u'renderLayerManager', u'defaultRenderLayer']

You can run mayapy interactively - effectively a command line version of maya - using the -i flag: This will start mayapy and give you a command prompt:

mayapy -i -c \"import maya.standalone; maya.standalone.initialize()\""

which again starts the standalone for you but keeps the session going instead of running a command and quitting.

To run a script file, just pass in the file as an argument. In that case you'd want to do as Kartik suggests and include the standalone.initalize() in the script. Then call it with

mayapy path/to/script.py

To suppress the userSetup, you can create an environmnet variable called MAYA_SKIP_USERSETUP_PY and set it to a non-zero value, that will load maya without running usersetup. You can also change environment varialbes or path variables before running the mayap; for example I can run mayapys from two different environments with these two bash aliases (in windows you'd use SET instead of EXPORT to change the env vars):

alias mp_zip="export MAYA_DEV=;mayapy -i -c \"import maya.standalone;    maya.standalone.initialize()\""
alias mp_std="export MAYA_DEV=C:/UL/tools/python/ulmaya;export ZOMBUILD='C:/ul/tools/python/dist/ulmaya.zip';mayapy -i -c \"import maya.standalone; maya.standalone.initialize()\""

This blog post includes a python module for spinning up Mayapy instances with different environments as needed.

If you want to interact with a running maya from another envrionment - say, if you're trying to remote control it from a handheld device or a C program - you can use the Maya commandPort to handle simple requests via TCP. For more complex situations you could set up a basic remoting service like this of your own, or use a pre-exiating python RPC module like RPyC or ZeroMQ

Answer 2

For something like this you can use Maya standalone instead of the full blown UI mode. It is faster. It is ideal for batch scheduled jobs like these. Maya standalone is just Maya running without the GUI. Once you have initialized your Maya standalone, you can import and call any scripts you want, as part of the original calling script. To start you off here is an example: (Feel free to use this as a reference/modify it to meet your needs)

In your script you first initialize Maya standalone.

import maya.standalone
maya.standalone.initialize("Python")

import maya.cmds as cmds
cmds.loadPlugin("Mayatomr") # Load all plugins you might need

That will get Maya running. Now we open and/or import all the files necessary (egs. lights, models etc.)

# full path to your Maya file to OPEN
maya_file_to_open = r"C:/Where/Ever/Your/Maya_Scene_Files/Are/your_main_maya_file.mb"

# Open your file
opened_file = cmds.file(maya_file_to_open, o=True)

# full path to your Maya file to IMPORT
maya_file_to_import = r"C:/Where/Ever/Your/Maya_Scene_Files/Are/your_maya_file.mb"

# Have a namespace if you want (recommended)
namespace = "SomeNamespaceThatIsNotAnnoying" 

# Import the file. the variable "nodes" will hold the names of all nodes imported, just in case.
nodes = cmds.file(maya_file_to_import, i=True,
                          renameAll=True,
                          mergeNamespacesOnClash=False,
                          namespace=namespace,
                          returnNewNodes=True,
                          options="v=0;",
                          type="mayaBinary" # any file type you want. this is just an example.
                          )

#TODO: Do all your scene setup/ positioning etc. if needed here...
#Tip: you can use cmds.viewFit(cam_name, fitFactor=1) to fit your camera on to selected objects

Now we save this file out and call Maya Batch renderer to render it out

render_file = "C:/Where/Ever/Your/Maya_Scene_Files/Are/your_RENDER_file.mb"
cmds.file(rename=render_file)
cmds.file(force=True, save=True, options='v=1;p=17', type='mayaBinary')

import sys
from os import path
from subprocess import Popen

render_project = r"C:/Where/Ever/YourRenderProjectFolder"
renderer_folder = path.split(sys.executable)[0]
renderer_exec_name = "Render"
params = [renderer_exec_name]
params += ['-percentRes', '75']
params += ['-alpha', '0']
params += ['-proj', render_project]
params += ['-r', 'mr']
params += [render_file]
p = Popen(params, cwd=renderer_folder)
stdout, stderr = p.communicate()

That's it! Of Course, your script will have to be run using Maya's Python interpreter (Mayapy).

Do check out the docs for all the commands used for more options, esp.: cmds.file() cmds.viewFit() cmds.loadPlugin() Subprocess and Popen

PLUS, because of the awesomeness of Python, you can use modules like sched (docs) to schedule the running of this method in your Python code.

Hope this was useful. Have fun with this. Cheers.