Update r2c export helper

scripts/export_r2c_layout.py

@@ -6,6 +6,7 @@ from __future__ import annotations
 import argparse
 import json
 import shutil
+from itertools import islice
 from pathlib import Path
 
 from datasets import load_dataset, load_from_disk
@@ -47,10 +48,22 @@ def main() -> None:
                     f_out.write(line)
 
     if args.local_stage_dir is None:
-        split_expr = {s: f"{s}[:{args.limit}]" if args.limit is not None else s for s in ("train", "validation", "test")}
-        ds = load_dataset(args.repo_id, "image_examples", split=split_expr, token=args.token)
-        if not isinstance(ds, dict):
-            ds = {"train": ds}
+        if args.limit is None:
+            split_expr = {s: s for s in ("train", "validation", "test")}
+            ds = load_dataset(args.repo_id, "image_examples", split=split_expr, token=args.token)
+            if not isinstance(ds, dict):
+                ds = {"train": ds}
+        else:
+            ds = {
+                split_name: load_dataset(
+                    args.repo_id,
+                    "image_examples",
+                    split=split_name,
+                    streaming=True,
+                    token=args.token,
+                )
+                for split_name in ("train", "validation", "test")
+            }
     else:
         local_ds = load_from_disk(args.local_stage_dir / "image_examples.dataset")
         ds = {}
@@ -59,7 +72,8 @@ def main() -> None:
 
     seen: set[str] = set()
     for split_name, split_ds in ds.items():
-        for row in tqdm(split_ds, desc=f"export {split_name} images"):
+        rows = islice(split_ds, args.limit) if args.limit is not None else split_ds
+        for row in tqdm(rows, desc=f"export {split_name} images", total=args.limit):
             img_fn = row["img_fn"]
             metadata_fn = row["metadata_fn"]