Update app.py

app.py

@@ -15,6 +15,7 @@ import lasio
 import os
 from typing import Optional, Tuple, Dict, Any, List
 import datetime
+import copy
 
 # ------------------------------------
 # CONFIGURATION & CONSTANTS
@@ -85,21 +86,31 @@ class DataManager:
         Converts DataFrame back to LAS format bytes for download.
         If original_las is provided, it preserves headers.
         """
+        new_las = lasio.LASFile()
+
         if original_las:
-            las = original_las
-            # Update data in LAS object
-            # Note: setting data in lasio can be tricky if shapes change
-            # We will construct a new LAS based on the old one's header to be safe
-            new_las = lasio.LASFile()
-            new_las.header = las.header
+            # FIX: Do not assign .header directly (read-only property).
+            # Instead, copy sections item by item.
+            
+            # Copy WELL information (Metadata)
+            for item in original_las.well:
+                # We use deepcopy to ensure we don't link to the session state object
+                new_las.well[item.mnemonic] = copy.deepcopy(item)
+            
+            # Copy PARAMETER information
+            for item in original_las.params:
+                new_las.params[item.mnemonic] = copy.deepcopy(item)
+                
+            # Copy Other info (often just text)
+            new_las.other = original_las.other
         else:
-            new_las = lasio.LASFile()
+            # Set default date if no original file
             new_las.well.DATE = str(datetime.datetime.now())
         
-        # Add curves
+        # Add curves from the DataFrame
         for col in df.columns:
-            # Check if curve exists to update, or add new
             unit = "UNKNOWN"
+            # Try to preserve units from original LAS if available
             if original_las:
                 for curve in original_las.curves:
                     if curve.mnemonic == col: