Python API


You can import the Python module as follows:

from pxr import Ar
from usdAssetResolver import FileResolver


Tokens can be found in FileResolver.Tokens:



We also have the opt-in feature to expose any identifier, regardless of absolute/relative/search path based formatting to be run through our mapped pairs mapping by setting the AR_CACHEDRESOLVER_ENV_EXPOSE_ABSOLUTE_PATH_IDENTIFIERS environment variable to 1 or by calling pxr.Ar.GetUnderlyingResolver().SetExposeAbsolutePathIdentifierState(True). This then forwards any path to be run through our mapped pairs mapping, regardless of how the identifier is formatted.

from pxr import Ar, Usd
from usdAssetResolver import FileResolver

file_resolver = Ar.GetUnderlyingResolver()

# Enable absolute identifier resolving
print("Resolver is currently exposing absolute path identifiers to the mapping pairs | {}".format(file_resolver.GetExposeAbsolutePathIdentifierState()))
# Or set the "AR_FILERESOLVER_ENV_EXPOSE_ABSOLUTE_PATH_IDENTIFIERS" environment variable to 1.
# This can't be done via Python, as it has to happen before the resolver is loaded.
file_resolver.GetExposeAbsolutePathIdentifierState() # Get the state of exposing absolute path identifiers
file_resolver.SetExposeAbsolutePathIdentifierState() # Set the state of exposing absolute path identifiers

Resolver Context

You can manipulate the resolver context (the object that holds the configuration the resolver uses to resolve paths) via Python in the following ways:

from pxr import Ar, Usd
from usdAssetResolver import FileResolver

# Get via stage
stage = Usd.Stage.Open("/some/stage.usd")
context_collection = stage.GetPathResolverContext()
fileResolver_context = context_collection.Get()[0]
# Or context creation
fileResolver_context = FileResolver.ResolverContext()

# To print a full list of exposed methods:
for attr in dir(FileResolver.ResolverContext):

Refreshing the Resolver Context


If you make changes to the context at runtime, you'll need to refresh it!

You can reload it as follows, that way the active stage gets the change notification.
from pxr import Ar
resolver = Ar.GetResolver()
context_collection = stage.GetPathResolverContext()
fileResolver_context = context_collection.Get()[0]
# Make edits as described below to the context.
fileResolver_context.AddMappingPair("source.usd", "destination.usd")
# Trigger Refresh (Some DCCs, like Houdini, additionally require node re-cooks.)

Search Paths

The search paths get read from the AR_SEARCH_PATHS env var by default. You can inspect and tweak the search paths at runtime by using the following methods:

ctx.GetSearchPaths()                        # Return all search paths (env and custom)
ctx.RefreshSearchPaths()                    # Reload env search paths and re-populates the search paths that the resolver uses. This must be called after changing the env var value or the custom search paths. 
ctx.GetEnvSearchPaths()                     # Return all env search paths 
ctx.GetCustomSearchPaths()                  # Return all custom search paths
ctx.SetCustomSearchPaths(searchPaths: list) # Set custom search paths

Mapping Pairs

To inspect/tweak the active mapping pairs, you can use the following:

ctx.GetMappingFilePath()                      # Get the mapping file path (Defaults file that the context created Resolver.CreateDefaultContextForAsset() opened)
ctx.SetMappingFilePath(p: str)                # Set the mapping file path
ctx.RefreshFromMappingFilePath()              # Reload mapping pairs from the mapping file path
ctx.GetMappingPairs()                         # Returns all mapping pairs as a dict
ctx.AddMappingPair(src: string, dst: str)     # Add a mapping pair
ctx.ClearMappingPairs()                       # Clear all mapping pairs
ctx.RemoveMappingByKey(src: str)              # Remove a mapping pair by key
ctx.RemoveMappingByValue(dst: str)            # Remove a mapping pair by value

To generate a mapping .usd file, you can do the following:

from pxr import Ar, Usd, Vt
from usdAssetResolver import FileResolver
stage = Usd.Stage.CreateNew('/some/path/mappingPairs.usda')
mapping_pairs = {'assets/assetA/assetA.usd':'assets/assetA/assetA_v005.usd', 'shots/shotA/shotA_v000.usd':'shots/shotA/shotA_v003.usd'}
mapping_array = []
for source_path, target_path in mapping_pairs.items():
    mapping_array.extend([source_path, target_path])
stage.SetMetadata('customLayerData', {FileResolver.Tokens.mappingPairs: Vt.StringArray(mapping_array)})

To change the asset path formatting before it is looked up in the mapping pairs, you can do the following:

ctx.GetMappingRegexExpression()               # Get the regex expression
ctx.SetMappingRegexExpression(regex_str: str) # Set the regex expression
ctx.GetMappingRegexFormat()                   # Get the regex expression substitution formatting
ctx.SetMappingRegexFormat(f: str)             # Set the regex expression substitution formatting