Allow steps_to_parquet.py to accept multiple ROOT input files

scripts/steps_to_parquet.py

@@ -5,6 +5,7 @@ Usage:
     uv run python steps_to_parquet.py input.root
     uv run python steps_to_parquet.py input.root -o output.parquet
     uv run python steps_to_parquet.py input.root --batch-size "200 MB" --tree Hits
+    uv run python steps_to_parquet.py input1.root input2.root input3.root
 """
 
 import argparse
@@ -86,9 +87,12 @@ def main() -> None:
     parser = argparse.ArgumentParser(
         description="Convert a Steps (or any flat+jagged) tree in a ROOT file to Parquet."
     )
-    parser.add_argument("root_file", help="Input ROOT file")
+    parser.add_argument("root_files", nargs="+", help="Input ROOT file(s)")
     parser.add_argument(
-        "-o", "--output", help="Output Parquet file (default: <input>.parquet)"
+        "-o",
+        "--output",
+        help="Output Parquet file (default: <input>.parquet). "
+        "Only valid with a single input file.",
     )
     parser.add_argument(
         "--batch-size",
@@ -108,13 +112,18 @@ def main() -> None:
     )
     args = parser.parse_args()
 
-    convert_steps_to_parquet(
-        args.root_file,
-        output_path=args.output,
-        batch_size=args.batch_size,
-        tree_name=args.tree,
-        compression="uncompressed" if args.compression == "none" else args.compression,
-    )
+    if args.output is not None and len(args.root_files) > 1:
+        parser.error("--output can only be used with a single input file")
+
+    compression = "uncompressed" if args.compression == "none" else args.compression
+    for root_file in args.root_files:
+        convert_steps_to_parquet(
+            root_file,
+            output_path=args.output,
+            batch_size=args.batch_size,
+            tree_name=args.tree,
+            compression=compression,
+        )
 
 
 if __name__ == "__main__":