Check if a Prim Exists

Certain functions may return a Usd.Prim object, but the Prim may not exist due to an incorrect path or because of changes on the Stage. You can use Usd.Object.IsValid() to check if the Prim is valid or exists.

USD Python

from pxr import Usd


def check_prim_exists(prim: Usd.Prim) -> bool:
    if prim.IsValid():
        return True
    return False

#############
# Full Usage
#############
from pxr import Sdf, UsdGeom

# Create an in-memory Stage with /World Xform prim as the default prim
stage: Usd.Stage = Usd.Stage.CreateInMemory()
default_prim: Usd.Prim = UsdGeom.Xform.Define(stage, Sdf.Path("/World")).GetPrim()
stage.SetDefaultPrim(default_prim)

# Create one prim and 
cube: Usd.Prim = UsdGeom.Cube.Define(stage, Sdf.Path("/World/Cube")).GetPrim()
empty_prim = Usd.Prim()

usda = stage.GetRootLayer().ExportToString()
print(usda)

# Check if prims exist
assert check_prim_exists(default_prim)
assert check_prim_exists(cube)
assert not check_prim_exists(empty_prim)

Alternatively, Usd.Object overrides the boolean operator so you can check with a simple boolean expression.

from pxr import Usd


def check_prim_exists(prim: Usd.Prim) -> bool:
    if prim:
        return True
    return False

#############
# Full Usage
#############
from pxr import Sdf, UsdGeom

# Create an in-memory Stage with /World Xform prim as the default prim
stage: Usd.Stage = Usd.Stage.CreateInMemory()
default_prim: Usd.Prim = UsdGeom.Xform.Define(stage, Sdf.Path("/World")).GetPrim()
stage.SetDefaultPrim(default_prim)

# Create one prim and 
cube: Usd.Prim = UsdGeom.Cube.Define(stage, Sdf.Path("/World/Cube")).GetPrim()
empty_prim = Usd.Prim()

usda = stage.GetRootLayer().ExportToString()
print(usda)

# Check if prims exist
assert check_prim_exists(default_prim)
assert check_prim_exists(cube)
assert not check_prim_exists(None)