Run Maya and execute a script

#1

How can I execute a python scripts after I launch Maya with subprocess

subprocess.Popen('C:/maya/maya.exe')

I need Maya with GUI. And the Python script I need to run is not static (and I don`t need to execute something all the time I run Maya), so I don’t think I can utilize userSetup.py.

I need to create/open asset/shot scenes from an external app, like Shotgun.

Run Nuke and execute a Python script
#2

So one option is to use the -command flag when launching maya, to run a mel command probably something like

subprocess.Popen(['C:/maya/maya.exe', '-command', "python('execfile(\"path_to_your_script\"')"])

Another would be to have a startup script that opens up the commandPort and then you can squirt commands through that to the running process.


has a pretty good example on how to set that up for sublime.

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#3

I can execute python code directly (without saving it to a file), right? Did not work for me:

cmd = [maya_exe, '-hideConsole', '-command', "python('print 'OLA' ')"]
subprocess.Popen(cmd)

// Error: python('print 'OLA' '); // 
// Error: Line 1.8: Syntax error //
#4

Try:
cmd = [maya_exe, '-hideConsole', '-command', "python(\"print 'OLA' \")"]

Mel basically has no idea about single quotes, so when passing in the python string you want it to eval, you have to wrap it in double quotes.

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#5

What if I need to pass an object (instance of a custom class)? It does not work, produce an error.

command = 'python(\"from maya_tools import asset_create; '\
                  'asset_create.run({}, {}) \")'\
                  .format(file_type_dict, asset_object)

cmd = [maya_exe, '-hideConsole',  '-command',  command]   
subprocess.Popen(cmd)

However, dictionaries, strings, integers are working fine.

#6

The way we’ve been handling that at work is by pickling. pickle is python’s generic object representation library, and allows you to easily write almost any object out to a file. https://docs.python.org/2.7/library/pickle.html

So gather all your data and pickle it in a temporary file. Then build the command for maya to unpickle that file, and pass that data to whatever function you want.

[Edit]
The biggest caveat is you have to make sure that whatever classes you have created are available using the same import statement both in and out of maya.

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#7

There’s a couple of ways around the nasty encoding issues that come with trying to run a commandline maya or mayapy.

Python support was bolted on after the fact so you have to indirect through mel. Rather than packing too much encoding into a command line (where it’s really easy to fatfinger something like a nested string encoding) one good trick is just to generate a mel file (temporary or permanent ) and pass that to the maya.

Keystone packs any arbitrary python you want into a mel file which can be run from the commandline. It’s designed for distributing an entire toolkit with multiple files, but it’d work for a single script if you wanted to do that.

If you have a simpler need to just pass some Python to maya without all the hassles, you can just steal the operative part of that like so:

import base64
import subprocess


def launch_maya(maya_path, python_script, *additional_args):

    encoded_python = base64.b64encode(python_script.encode('utf-8'))
    script_text = '''python("import base64; exec (base64.urlsafe_b64decode({}))")'''
    args = [maya_path, '-c', script_text.format(encoded_python)]
    args.extend(str(i) for i in additional_args)
    subprocess.check_call(args)


launch_maya('c:/program files/autodesk/maya2018/bin/maya.exe', 'import sys; print("hello world " * int(sys.argv[-1]))', 7)

In this version python_script is the text of whatever python you want to run; you could just read it from a file if you wanted to.

If you pass additional arguments to the command line they show up in sys.argv so you can get at them (as in the example above) – they will all be strings, but you can pass any string you want.

If you plan on reusing the same script, you could convert the above function to generate a mel script that included the encoded python – that would make it double-clickable. That’s how Keystone works.

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