USD simple print diff of dirty layer in memory to the original state on disk.

usd_print_simple_diff_to_layer_on_disk.py

import difflib

from pxr import Sdf

# Purely as an example, say this `layer` is one that's currently already
# available and is dirty currently
identifier = r"C:\Users\User\Desktop\asset.usd"
layer = Sdf.Layer.FindOrOpen(identifier)
layer.Reload()  # just so we can re-run this script  
layer.subLayerPaths.append("./hello_world.usd")  # making a change, making it dirty


# Now re-open the layer from disk (anonymous, as a copy)
# And then do a text-diff between the two
layer_as_original = Sdf.Layer.OpenAsAnonymous(identifier)
changed_ascii = layer.ExportToString()
original_ascii = layer_as_original.ExportToString()


# Print diff
for line in difflib.unified_diff(
    original_ascii.splitlines(), 
    changed_ascii.splitlines(),
    tofile=f"{layer.identifier} (changed)",
    fromfile=f"{layer.identifier} (on disk)",
    lineterm=""
):
    print(line)

Example output to the above script:

--- c:/Users/User/Desktop/asset.usd (on disk)
+++ c:/Users/User/Desktop/asset.usd (changed)
@@ -1,4 +1,9 @@
 #usda 1.0
+(
+    subLayers = [
+        @./hello_world.usd@
+    ]
+)
 
 def Scope "asset" (
     kind = "group"