convertTreeToRNTuple Namespace Reference

Functions
bool	convert_tree_to_rntuple (input_file, tree_name, output_file, ntuple_name)
int	main ()

Detailed Description

Convert TTree to RNTuple using ROOT's RNTupleImporter.

This script imports TTrees from ROOT files and converts them to RNTuple format,
which provides better compression, faster I/O, and modern columnar storage.

Usage:
    python convertTreeToRNTuple.py -f input.root -t cbmsim -o output.root -n fairdata
    python convertTreeToRNTuple.py -f input.root  # Uses default tree/ntuple names

Note:
    RNTuple has some limitations compared to TTree:
    - TObjArray and other legacy ROOT containers cannot be stored natively
    - Use std::vector instead of TObjArray for RNTuple compatibility
    - TClonesArray is also not supported; migrate to std::vector

Function Documentation

convert_tree_to_rntuple()

bool convertTreeToRNTuple.convert_tree_to_rntuple	(		input_file,
			tree_name,
			output_file,
			ntuple_name
	)

Convert a TTree to RNTuple format.

Args:
    input_file: Path to input ROOT file containing TTree
    tree_name: Name of the TTree to convert
    output_file: Path to output ROOT file for RNTuple
    ntuple_name: Name for the output RNTuple

Definition at line 27 of file convertTreeToRNTuple.py.

def convert_tree_to_rntuple(input_file, tree_name, output_file, ntuple_name) -> bool:
    """
    Convert a TTree to RNTuple format.
 
    Args:
        input_file: Path to input ROOT file containing TTree
        tree_name: Name of the TTree to convert
        output_file: Path to output ROOT file for RNTuple
        ntuple_name: Name for the output RNTuple
    """
    print("Converting TTree → RNTuple")
    print(f"  Input:  {input_file}:{tree_name}")
    print(f"  Output: {output_file}:{ntuple_name}")
    print()
 
    with ROOT.TFile.Open(input_file, "READ") as input_root_file:
        tree = input_root_file.Get(tree_name)
        if not tree:
            print(f"ERROR: Tree '{tree_name}' not found in {input_file}")
            print("Available trees:")
            for key in input_root_file.GetListOfKeys():
                obj = key.ReadObj()
                if obj.InheritsFrom("TTree"):
                    print(f"  - {key.GetName()}")
            return False
 
        num_entries = tree.GetEntries()
        print(f"Found TTree '{tree_name}' with {num_entries} entries")
        print()
 
    # Convert using RNTupleImporter
    try:
        importer = ROOT.ROOT.Experimental.RNTupleImporter.Create(input_file, tree_name, output_file)
 
        if not importer:
            print("ERROR: Failed to create RNTupleImporter")
            return False
 
        # Set the RNTuple name (defaults to tree name if not set)
        importer.SetNTupleName(ntuple_name)
 
        # Optional: Configure import options
        # importer.SetMaxUnzippedPageSize(...)  # Adjust page size if needed
        # importer.SetCompressionSettings(...)  # Adjust compression (default: zstd)
 
        print("Starting conversion...")
        importer.Import()  # Import() throws exception on failure
 
        print("✓ Conversion complete!")
        print()
 
        # Verify output
        with ROOT.TFile.Open(output_file, "READ"):
            reader = ROOT.ROOT.RNTupleReader.Open(ntuple_name, output_file)
            num_rntuple_entries = reader.GetNEntries()
 
            print("Verification:")
            print(f"  TTree entries:   {num_entries}")
            print(f"  RNTuple entries: {num_rntuple_entries}")
 
            if num_entries == num_rntuple_entries:
                print("  ✓ Entry count matches")
            else:
                print("  ✗ WARNING: Entry count mismatch!")
 
        return True
 
    except Exception as e:
        print(f"ERROR: Exception during conversion: {e}")
        import traceback
 
        traceback.print_exc()
        return False
 
 

main()

int convertTreeToRNTuple.main

(

void

)

Parse arguments and run the TTree to RNTuple conversion.

Definition at line 102 of file convertTreeToRNTuple.py.

def main() -> int:
    """Parse arguments and run the TTree to RNTuple conversion."""
    parser = argparse.ArgumentParser(
        description="Convert TTree to RNTuple using ROOT's RNTupleImporter",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog="""
Examples:
  # Convert cbmsim tree to fairdata RNTuple
  %(prog)s -f ship.conical.Pythia8-TGeant4.root -t cbmsim -o output.root -n fairdata
 
  # Use defaults (cbmsim → fairdata)
  %(prog)s -f ship.conical.Pythia8-TGeant4.root
 
  # Convert custom tree
  %(prog)s -f mydata.root -t mytree -o converted.root -n myntuple
        """,
    )
 
    parser.add_argument("-f", "--input-file", required=True, help="Input ROOT file containing TTree")
    parser.add_argument(
        "-t",
        "--tree-name",
        default="cbmsim",
        help="Name of TTree to convert (default: cbmsim)",
    )
    parser.add_argument(
        "-o",
        "--output-file",
        default=None,
        help="Output ROOT file for RNTuple (default: <input>_rntuple.root)",
    )
    parser.add_argument(
        "-n",
        "--ntuple-name",
        default="fairdata",
        help="Name for output RNTuple (default: fairdata)",
    )
 
    args = parser.parse_args()
 
    if args.output_file is None:
        if args.input_file.endswith(".root"):
            args.output_file = args.input_file.replace(".root", "_rntuple.root")
        else:
            args.output_file = args.input_file + "_rntuple.root"
 
    success = convert_tree_to_rntuple(args.input_file, args.tree_name, args.output_file, args.ntuple_name)
 
    if success:
        print()
        print("Success! RNTuple file created:")
        print(f"  {args.output_file}")
        return 0
    else:
        print()
        print("Conversion failed!")
        return 1