Maya Python Metadata Utils

A simple solution for storing python objects as data on a node in Maya.

Lots of metadata solutions involve wrapping the complex nature of Maya's node attribute types and quirks to allow easy storing and retrieving of data, and connecting nodes via message attributes. PyMetaNode aims to avoid (most of) maya's attributes altogether for simplicity and flexibility. This places the responsibility of controlling data structures completely on the tools, and treats the nodes purely as storage.

There are several advantages of using Maya nodes for storing data vs. alternate methods, such as not requiring any other files other than the maya scene containing the node, and the ability to undo and redo changes in nodes, and therefore changes in data.

Features

• Store basic python object types (any type supported by python's ast.literal_eval).
• Store references to other nodes inside metadata.
• Store data for multiple meta classes on a single node.
• Find any node with metadata.
• Find nodes with metadata for a specific metaclass.
• Works with or without PyMel.
• A concise and straightforward api, no custom plugin nodes to store data.
• Fast, uses Maya api for all critical operations.

Installation

• Download the latest release
• Unzip and copy the contents to:
  • Windows: ~/Documents/maya/modules/
  • Mac: ~/Library/Preferences/Autodesk/maya/modules/
  • Linux: ~/maya/modules/

Note that you may need to create the modules folder if it does not exist.

Once installed, the result should look like this:

.../maya/modules/pymetanode/
.../maya/modules/pymetanode.mod

Basic Usage

PyMel is supported if available. If not, then functions will expect node names as string or api MObjects:

import pymel.core as pm

# get selected node via PyMel
node = pm.selected()[0]

or

from maya import cmds

# get selected node via cmds
node = cmds.ls(selection=True)[0]

Then store any basic python data types, serialized as strings, on the given node:

import pymetanode as meta

# create some example data
my_data = {"myList": [1, 2, 3], "myTitle": "ABC"}
# data must be associated with a metaclass
my_meta_class = "MyMetaClass"

# set meta data on the node
meta.set_metadata(node, my_meta_class, my_data)

# retrieve the stored data for 'MyMetaClass' only
# result: {"myList":[1,2,3], "myTitle":"ABC"}
meta.get_metadata(node, my_meta_class)

# retrieve all metadata on the node
# result: {"MyMetaClass": {"myList":[1,2,3], "myTitle":"ABC"}}
meta.get_metadata(node)

# check if a node has meta data for a meta class
# result: True
meta.has_metaclass(node, "MyMetaClass")

# check if a node has any meta data
# result: True
meta.is_meta_node(node)

# find all nodes in the scene that have metadata for a class
meta.find_meta_nodes("MyMetaClass")

How does it work

The implementation is very simple: python data is serialized into a string that is stored on a Maya node, and deserialized using ast.literal_eval when retrieved. Each 'metaclass' type adds an attribute on the node that is used to perform fast searching for nodes by the existence of that attribute. Data goes through a basic encoding and decoding that allows node references and other possible features.

PyMel vs cmds

When you import pymetanode it tests for the existence of pymel and, if available, imports a pymel version of the api that accepts PyNode, str, and MObjects for all node arguments. If PyMel isn't available, the default api is imported which supports nodes as str or MObject.

Running Tests

• Add mayapy directory to PATH environment variable.
• From the root directory of this repository, run setup.sh test