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Publishing workflow consists of 2 parts:

  • Creating - Mark what will be published and how.
  • Publishing - Use data from Creating to go through the pyblish process.

OpenPype is using pyblish for the publishing process. OpenPype extends and modifies its few functions a bit, mainly for reports and UI purposes. The main differences are that OpenPype's publish UI allows to enable/disable instances or plugins during Creating part instead of in the publishing part and has limited plugin actions only for failed validation plugins.


Concept of Creating does not have to "create" anything yet, but prepare and store metadata about an "instance" (becomes a subset after the publish process). Created instance always has family which defines what kind of data will be published, the best example is workfile family. Storing of metadata is host specific and may be even a Creator plugin specific. Most hosts are storing metadata into a workfile (Maya scene, Nuke script, etc.) to an item or a node the same way as regular Pyblish instances, so consistency of host implementation is kept, but some features may require a different approach that is the reason why it is creator plugin responsibility. Storing the metadata to the workfile persists values, so the artist does not have to create and set what should be published and how over and over.

Created instance

Objected representation of created instance metadata defined by class CreatedInstance. Has access to CreateContext and BaseCreator that initialized the object. Is a dictionary-like object with few immutable keys (marked with start * in table). The immutable keys are set by the creator plugin or create context on initialization and their values can't change. Instance can have more arbitrary data, for example ids of nodes in scene but keep in mind that some keys are reserved.

*idstrIdentifier of metadata type. ATM constant "pyblish.avalon.instance"
*instance_idstrUnique ID of instance. Set automatically on instance creation using str(uuid.uuid4())
*familystrInstance's family representing type defined by creator plugin.
*creator_identifierstrIdentifier of creator that collected/created the instance.
*creator_attributesdictDictionary of attributes that are defined by the creator plugin (get_instance_attr_defs).
*publish_attributesdictDictionary of attributes that are defined by publish plugins.
variantstrVariant is entered by the artist on creation and may affect subset.
subsetstrName of instance. This name will be used as a subset name during publishing. Can be changed on context change or variant change.
activeboolIs the instance active and will be published or not.
assetstrName of asset in which context was created.
taskstrName of task in which context was created. Can be set to None.

Task should not be required until the subset name template expects it.

object of CreatedInstance has method data_to_store which returns a dictionary that can be parsed to a json string. This method will return all data related to the instance so it can be re-created using CreatedInstance.from_existing(data).

Controller and wrapper around Creating is CreateContext which cares about loading of plugins needed for Creating. And validates required functions in host implementation.

Context discovers creator and publish plugins. Trigger collections of existing instances on creators and trigger Creating itself. Also it keeps in mind instance objects by their ids.

Creator plugins can call creator_adds_instance or creator_removed_instance to add/remove instances but these methods are not meant to be called directly out of the creator. The reason is that it is the creator's responsibility to remove metadata or decide if it should remove the instance.

Required functions in host implementation

Host implementation must implement get_context_data and update_context_data. These two functions are needed to store metadata that are not related to any instance but are needed for Creating and publishing process. Right now only data about enabled/disabled optional publish plugins is stored there. When data is not stored and loaded properly, reset of publishing will cause that they will be set to default value. Context data also parsed to json string similarly as instance data.

There are also few optional functions. For UI purposes it is possible to implement get_context_title which can return a string shown in UI as a title. Output string may contain html tags. It is recommended to return context path (it will be created function this purposes) in this order "{project name}/{asset hierarchy}/<b>{asset name}</b>/{task name}".

Another optional function is get_current_context. This function is handy in hosts where it is possible to open multiple workfiles in one process so using global context variables is not relevant because artists can switch between opened workfiles without being acknowledged. When a function is not implemented or won't return the right keys the global context is used.

# Expected keys in output
"project_name": "MyProject",
"asset_name": "sq01_sh0010",
"task_name": "Modeling"

Create plugin

Main responsibility of create plugin is to create, update, collect and remove instance metadata and propagate changes to create context. Has access to CreateContext (self.create_context) that discovered the plugin so has also access to other creators and instances. Create plugins have a lot of responsibility so it is recommended to implement common code per host.


Base implementation of creator plugin. It is not recommended to use this class as base for production plugins but rather use one of HiddenCreator, AutoCreator and Creator variants.


  • family (class attr) - Tells what kind of instance will be created.
class WorkfileCreator(Creator):
family = "workfile"
  • collect_instances (method) - Collect already existing instances from the workfile and add them to create context. This method is called on initialization or reset of CreateContext. Each creator is responsible to find its instance metadata, convert them to CreatedInstance object and add them to create context (self._add_instance_to_context(instnace_obj)).
def collect_instances(self):
# Using 'pipeline.list_instances' is just example how to get existing instances from scene
# - getting existing instances is different per host implementation
for instance_data in pipeline.list_instances():
# Process only instances that were created by this creator
creator_id = instance_data.get("creator_identifier")
if creator_id == self.identifier:
# Create instance object from existing data
instance = CreatedInstance.from_existing(
instance_data, self
# Add instance to create context
  • create (method) - Create a new object of CreatedInstance store its metadata to the workfile and add the instance into the created context. Failed Creating should raise CreatorError if an error happens that artists can fix or give them some useful information. Triggers and implementation differs for Creator, HiddenCreator and AutoCreator.

  • update_instances (method) - Update data of instances. Receives tuple with instance and changes.

def update_instances(self, update_list):
# Loop over changed instances
for instance, changes in update_list:
# Example possible usage of 'changes' to use different node on change
# of node id in instance data (MADE UP)
node = None
if "node_id" in changes:
old_value, new_value = changes["node_id"]
if new_value is not None:
node = pipeline.get_node_by_id(new_value)

if node is None:
node = pipeline.get_node_by_instance_id(
# Get node in scene that represents the instance
# Imprind data to a node
pipeline.imprint(node, instance.data_to_store())

# Most implementations will probably ignore 'changes' completely
def update_instances(self, update_list):
for instance, _ in update_list:
# Get node from scene
node = pipeline.get_node_by_instance_id(
# Imprint data to node
pipeline.imprint(node, instance.data_to_store())
  • remove_instances (method) - Remove instance metadata from workfile and from create context.
# Possible way how to remove instance
def remove_instances(self, instances):
for instance in instances:
# Remove instance metadata from workflle
# Remove instance from create context

# Default implementation of `AutoCreator`
def remove_instances(self, instances):

When host implementation use universal way how to store and load instances you should implement host specific creator plugin base class with implemented collect_instances, update_instances and remove_instances.

Optional implementations

  • enabled (attr) - Boolean if the creator plugin is enabled and used.
  • identifier (class attr) - Consistent unique string identifier of the creator plugin. Is used to identify source plugin of existing instances. There can't be 2 creator plugins with the same identifier. Default implementation returns family attribute.
class RenderLayerCreator(Creator):
family = "render"
identifier = "render_layer"

class RenderPassCreator(Creator):
family = "render"
identifier = "render_pass"
  • label (attr) - String label of creator plugin which will show up in UI, identifier is used when not set. It should be possible to use html tags.
class RenderLayerCreator(Creator):
label = "Render Layer"
  • get_icon (attr) - Icon of creator and its instances. Value can be a path to an image file, full name of qtawesome icon, QPixmap or QIcon. For complex cases or cases when Qt objects are returned it is recommended to override get_icon method and handle the logic or import Qt inside the method to not break headless usage of creator plugin. For list of qtawesome icons check qtawesome github repository (look for the used version in pyproject.toml). Default implementation return icon attribute.
  • icon (method) - Attribute for default implementation of get_icon.
class RenderLayerCreator(Creator):
# Use font awesome 5 icon
icon = "fa5.building"
  • get_instance_attr_defs (method) - Attribute definitions of instance. Creator can define attribute values with default values for each instance. These attributes may affect how instances will be instance processed during publishing. Attribute defiitions can be used from openpype.lib.attribute_definitions. Attribute definitions define basic types of values for different cases e.g. boolean, number, string, enumerator, etc. Default implementation returns instance_attr_defs.
  • instance_attr_defs (attr) - Attribute for default implementation of get_instance_attr_defs.
from openpype.lib import attribute_definitions

class RenderLayerCreator(Creator):
def get_instance_attr_defs(self):
# Return empty list if '_allow_farm_render' is not enabled (can be set during initialization)
if not self._allow_farm_render:
return []
# Give artist option to change if should be rendered on farm or locally
return [
label="Render on Farm"
  • get_subset_name (method) - Calculate subset name based on passed data. Data can be extended using the get_dynamic_data method. Default implementation is using get_subset_name from openpype.lib which is recommended.

  • get_dynamic_data (method) - Can be used to extend data for subset templates which may be required in some cases.


Creator which is not showed in UI so artist can't trigger it directly but is available for other creators. This creator is primarily meant for cases when creation should create different types of instances. For example during editorial publishing where input is single edl file but should create 2 or more kind of instances each with different family, attributes and abilities. Arguments for creation were limited to instance_data and source_data. Data of instance_data should follow what is sent to other creators and source_data can be used to send custom data defined by main creator. It is expected that HiddenCreator has specific main or "parent" creator.

def create(self, instance_data, source_data):
variant = instance_data["variant"]
task_name = instance_data["task"]
asset_name = instance_data["asset"]
asset_doc = get_asset_by_name(self.project_name, asset_name)
variant, task_name, asset_doc, self.project_name, self.host_name)


Creator that is triggered on reset of create context. Can be used for families that are expected to be created automatically without artist interaction (e.g. workfile). Method create is triggered after collecting all creators.


AutoCreator has implemented remove_instances to do nothing as removing of auto created instances would lead to creating new instance immediately or on refresh.

def __init__(
self, create_context, system_settings, project_settings, *args, **kwargs
super(MyCreator, self).__init__(
create_context, system_settings, project_settings, *args, **kwargs
# Get variant value from settings
variant_name = (
if not variant_name:
variant_name = "Main"
self._variant_name = variant_name

# Create does not expect any arguments
def create(self):
# Look for existing instance in create context
existing_instance = None
for instance in self.create_context.instances:
if instance.creator_identifier == self.identifier:
existing_instance = instance

# Collect current context information
# - variant can be filled from settings
variant = self._variant_name
# Only place where we can look for current context
project_name = self.project_name
asset_name = legacy_io.Session["AVALON_ASSET"]
task_name = legacy_io.Session["AVALON_TASK"]
host_name = legacy_io.Session["AVALON_APP"]

# Create new instance if does not exist yet
if existing_instance is None:
asset_doc = get_asset_by_name(project_name, asset_name)
subset_name = self.get_subset_name(
variant, task_name, asset_doc, project_name, host_name
data = {
"asset": asset_name,
"task": task_name,
"variant": variant
variant, task_name, asset_doc, project_name, host_name

new_instance = CreatedInstance(, subset_name, data, self

# Update instance context if is not the same
elif (
existing_instance["asset"] != asset_name
or existing_instance["task"] != task_name
asset_doc = get_asset_by_name(project_name, asset_name)
subset_name = self.get_subset_name(
variant, task_name, asset_doc, project_name, host_name
existing_instance["asset"] = asset_name
existing_instance["task"] = task_name


Implementation of creator plugin that is triggered manually by the artist in UI (or by code). Has extended options for UI purposes than AutoCreator and create method expect more arguments.

Optional implementations

  • create_allow_context_change (class attr) - Allow to set context in UI before Creating. Some creators may not allow it or their logic would not use the context selection (e.g. bulk creators). Is set to True but default.
class BulkRenderCreator(Creator):
create_allow_context_change = False
  • get_default_variants (method) - Returns list of default variants that are listed in create dialog for user. Returns default_variants attribute by default.

  • default_variants (attr) - Attribute for default implementation of get_default_variants.

  • get_default_variant (method) - Returns default variant that is prefilled in UI (value does not have to be in default variants). By default returns default_variant attribute. If returns None then UI logic will take first item from get_default_variants if there is any otherwise "Main" is used.

  • default_variant (attr) - Attribute for default implementation of get_default_variant.

  • get_description (method) - Returns a short string description of the creator. Returns description attribute by default.

  • description (attr) - Attribute for default implementation of get_description.

  • get_detailed_description (method) - Returns detailed string description of creator. Can contain markdown. Returns detailed_description attribute by default.

  • detailed_description (attr) - Attribute for default implementation of get_detailed_description.

  • get_pre_create_attr_defs (method) - Similar to get_instance_attr_defs returns attribute definitions but they are filled before creation. When creation is called from UI the values are passed to create method. Returns pre_create_attr_defs attribute by default.

  • pre_create_attr_defs (attr) - Attribute for default implementation of get_pre_create_attr_defs.

from openpype.lib import attribute_definitions
from openpype.pipeline.create import Creator

class CreateRender(Creator):
family = "render"
label = "Render"
icon = "fa.eye"
description = "Render scene viewport"

def __init__(
self, context, system_settings, project_settings, *args, **kwargs
super(CreateRender, self).__init__(
context, system_settings, project_settings, *args, **kwargs
plugin_settings = (
# Get information if studio has enabled farm publishing
self._allow_farm_render = plugin_settings["allow_farm_render"]
# Get default variants from settings
self.default_variants = plugin_settings["variants"]

def get_instance_attr_defs(self):
# Return empty list if '_allow_farm_render' is not enabled (can be set during initialization)
if not self._allow_farm_render:
return []
# Give artist option to change if should be rendered on farm or locally
return [
label="Render on Farm"

def get_pre_create_attr_defs(self):
# Give user option to use selection or not
attrs = [
label="Use selection"
if self._allow_farm_render:
# Set to render on farm in creator dialog
# - this value is not automatically passed to instance attributes
# creator must do that during creation
label="Render on Farm"
return attrs

def create(self, subset_name, instance_data, pre_create_data):
# - 'subset_name' - precalculated subset name
# - 'instance_data' - context data
# - 'asset' - asset name
# - 'task' - task name
# - 'variant' - variant
# - 'family' - instnace family

# Check if should use selection or not
if pre_create_data.get("use_selection"):
items = pipeline.get_selection()
items = [pipeline.create_write()]

# Validations related to selection
if len(items) > 1:
raise CreatorError("Please select only single item at time.")

elif not items:
raise CreatorError("Nothing to create. Select at least one item.")

# Create instence object
new_instance = CreatedInstance(, subset_name, data, self)
# Pass value from pre create attribute to instance
# - use them only when pre create date contain the data
if "render_farm" in pre_create_data:
use_farm = pre_create_data["render_farm"]
new_instance.creator_attributes["render_farm"] = use_farm

# Store metadata to workfile
pipeline.imprint(, new_instance.data_to_store())

# Add instance to context



OpenPype define few specific exceptions that should be used in publish plugins.

Validation exception

Validation plugins should raise PublishValidationError to show to an artist what's wrong and give him actions to fix it. The exception says that errors in the plugin can be fixed by the artist himself (with or without action on plugin). Any other errors will stop publishing immediately. The exception PublishValidationError raised after validation order has the same effect as any other exception.

Exception PublishValidationError expects 4 arguments:

  • message Which is not used in UI but for headless publishing.
  • title Short description of error (2-5 words). Title is used for grouping of exceptions per plugin.
  • description Detailed description of the issue where markdown and html can be used.
  • detail Is optional to give even more detailed information for advanced users. At this moment the detail is shown directly under description but it is in plan to have detail in a collapsible widget.

Extended version is PublishXmlValidationError which uses xml files with stored descriptions. This helps to avoid having huge markdown texts inside code. The exception has 4 arguments:

  • plugin The plugin object which raises the exception to find its related xml file.
  • message Exception message for publishing without UI or different pyblish UI.
  • key Optional argument says which error from xml is used as a validation plugin may raise error with different messages based on the current errors. Default is "main".
  • formatting_data Optional dictionary to format data in the error. This is used to fill detailed description with data from the publishing so artist can get more precise information.

Where and how to create xml file

Xml files for PublishXmlValidationError must be located in ./help subfolder next to the plugin and the filename must match the filename of the plugin.

# File location related to plugin file
└ publish
├ help
│ ├ validate_scene.xml
│ └ ...
└ ...

Xml file content has <root> node which may contain any amount of <error> nodes, but each of them must have id attribute with unique value. That is then used for key. Each error must have <title> and <description> and <detail>. Text content may contain python formatting keys that can be filled when an exception is raised.

<?xml version="1.0" encoding="UTF-8"?>
<error id="main">
<title>Subset context</title>
<description>## Invalid subset context

Context of the given subset doesn't match your current scene.

### How to repair?

You can fix this with the "Repair" button on the right. This will use '{expected_asset}' asset name and overwrite '{found_asset}' asset name in scene metadata.

After that restart publishing with Reload button.
### How could this happen?

The subset was created in different scene with different context
or the scene file was copy pasted from different context.

Known errors

When there is a known error that can't be fixed by the user (e.g. can't connect to deadline service, etc.) KnownPublishError should be raised. The only difference is that its message is shown in UI to the artist otherwise a neutral message without context is shown.

Plugin extension

Publish plugins can be extended by additional logic when inheriting from OpenPypePyblishPluginMixin which can be used as mixin (additional inheritance of class). Publish plugins that inherit from this mixin can define attributes that will be shown in CreatedInstance. One of the most important usages is to be able turn on/off optional plugins.

Attributes are defined by the return value of get_attribute_defs method. Attribute definitions are for families defined in plugin's families attribute if it's instance plugin or for whole context if it's context plugin. To convert existing values (or to remove legacy values) can be re-implemented convert_attribute_values. Default implementation just converts the values to right types.

:::Important Values of publish attributes from created instance are never removed automatically so implementing this method is the best way to remove legacy data or convert them to new data structure. :::

Possible attribute definitions can be found in openpype/pipeline/lib/

Example plugin

import pyblish.api
from openpype.lib import attribute_definitions
from openpype.pipeline import OpenPypePyblishPluginMixin

# Example context plugin
class MyExtendedPlugin(
pyblish.api.ContextPlugin, OpenPypePyblishPluginMixin
optional = True
active = True

def get_attribute_defs(cls):
return [
# Key under which it will be stored
# Use 'active' as default value,
# Use plugin label as label for attribute

def process_plugin(self, context):
# First check if plugin is optional
if not self.optional:
return True

# Attribute values are stored by class names
# - for those purposes was implemented 'get_attr_values_from_data'
# to help with accessing it
attribute_values = self.get_attr_values_from_data(
# Get 'process' key
process_value = attribute_values.get("process")
if process_value is None or process_value:
return True
return False

def process(self, context):
if not self.process_plugin(context):
# Do plugin logic

UI examples

Main publish window

Main window of publisher shows instances and their values, collected by creators.

Card view Publisher UI - Card view List view Publisher UI - List view

Instances views

List of instances always contains an Options item which is used to show attributes of context plugins. Values from the item are saved and loaded using host implementation get_context_data and update_context_data. Instances are grouped by family and can be shown in card view (single selection) or list view (multi selection).

Instance view has at the bottom 3 buttons. Plus sign opens create dialog, bin removes selected instances and stripes swap card and list view.

Context options

It is possible to change variant or asset and task context of instances at the top part but all changes there must be confirmed. Confirmation will trigger recalculation of subset names and all new data are stored to instances.

Create attributes

Instance attributes display all created attributes of all selected instances. All attributes that have the same definition are grouped into one input and are visually indicated if values are not the same for selected instances. In most cases have < Multiselection > placeholder.

Publish attributes

Publish attributes work the same way as create attributes but the source of attribute definitions are pyblish plugins. Attributes are filtered based on families of selected instances and families defined in the pyblish plugin.

Create dialog

Publisher UI - Create dialog Create dialog is used by artist to create new instances in a context. The context selection can be enabled/disabled by changing create_allow_context_change on creator plugin. In the middle part the artist selects what will be created and what variant it is. On the right side is information about the selected creator and its pre-create attributes. There is also a question mark button which extends the window and displays more detailed information about the creator.