finish examples 2 and 3

lerobot/common/datasets/abstract.py

@@ -59,6 +59,8 @@ class AbstractDataset(TensorDictReplayBuffer):
         collate_fn: Callable | None = None,
         writer: Writer | None = None,
         transform: "torchrl.envs.Transform" = None,
+        # Don't actually load any data. This is a stand-in solution to get the transforms.
+        dummy: bool = False,
     ):
         assert (
             self.available_datasets is not None
@@ -77,7 +79,7 @@ class AbstractDataset(TensorDictReplayBuffer):
                 f"The version of the dataset ({self.version}) is not enforced when root is provided ({self.root})."
             )
 
-        storage = self._download_or_load_dataset()
+        storage = self._download_or_load_dataset() if not dummy else None
 
         super().__init__(
             storage=storage,

lerobot/common/datasets/aloha.py

@@ -97,6 +97,7 @@ class AlohaDataset(AbstractDataset):
         collate_fn: Callable | None = None,
         writer: Writer | None = None,
         transform: "torchrl.envs.Transform" = None,
+        dummy: bool = False,
     ):
         super().__init__(
             dataset_id,
@@ -110,6 +111,7 @@ class AlohaDataset(AbstractDataset):
             collate_fn=collate_fn,
             writer=writer,
             transform=transform,
+            dummy=dummy,
         )
 
     @property

lerobot/common/datasets/factory.py

@@ -21,7 +21,12 @@ def make_offline_buffer(
     overwrite_batch_size=None,
     overwrite_prefetch=None,
     stats_path=None,
+    # Don't actually load any data. This is a stand-in solution to get the transforms.
+    dummy=False,
 ):
+    if dummy and normalize and stats_path is None:
+        raise ValueError("`stats_path` is required if `dummy` and `normalize` are True.")
+
     if cfg.policy.balanced_sampling:
         assert cfg.online_steps > 0
         batch_size = None
@@ -93,6 +98,7 @@ def make_offline_buffer(
         root=DATA_DIR,
         pin_memory=pin_memory,
         prefetch=prefetch if isinstance(prefetch, int) else None,
+        dummy=dummy,
     )
 
     if cfg.policy.name == "tdmpc":

lerobot/common/datasets/pusht.py

@@ -100,6 +100,7 @@ class PushtDataset(AbstractDataset):
         collate_fn: Callable | None = None,
         writer: Writer | None = None,
         transform: "torchrl.envs.Transform" = None,
+        dummy: bool = False,
     ):
         super().__init__(
             dataset_id,
@@ -113,6 +114,7 @@ class PushtDataset(AbstractDataset):
             collate_fn=collate_fn,
             writer=writer,
             transform=transform,
+            dummy=dummy,
         )
 
     def _download_and_preproc_obsolete(self):

lerobot/common/datasets/simxarm.py

@@ -51,6 +51,7 @@ class SimxarmDataset(AbstractDataset):
         collate_fn: Callable | None = None,
         writer: Writer | None = None,
         transform: "torchrl.envs.Transform" = None,
+        dummy: bool = False,
     ):
         super().__init__(
             dataset_id,
@@ -64,6 +65,7 @@ class SimxarmDataset(AbstractDataset):
             collate_fn=collate_fn,
             writer=writer,
             transform=transform,
+            dummy=dummy,
         )
 
     def _download_and_preproc_obsolete(self):

lerobot/common/utils.py

@@ -1,9 +1,13 @@
 import logging
+import os.path as osp
 import random
 from datetime import datetime
+from pathlib import Path
 
+import hydra
 import numpy as np
 import torch
+from omegaconf import DictConfig
 
 
 def get_safe_torch_device(cfg_device: str, log: bool = False) -> torch.device:
@@ -63,3 +67,29 @@ def format_big_number(num):
         num /= divisor
 
     return num
+
+
+def _relative_path_between(path1: Path, path2: Path) -> Path:
+    """Returns path1 relative to path2."""
+    path1 = path1.absolute()
+    path2 = path2.absolute()
+    try:
+        return path1.relative_to(path2)
+    except ValueError:  # most likely because path1 is not a subpath of path2
+        common_parts = Path(osp.commonpath([path1, path2])).parts
+        return Path(
+            "/".join([".."] * (len(path2.parts) - len(common_parts)) + list(path1.parts[len(common_parts) :]))
+        )
+
+
+def init_hydra_config(config_path: str, overrides: list[str] | None = None) -> DictConfig:
+    """Initialize a Hydra config given only the path to the relevant config file.
+
+    For config resolution, it is assumed that the config file's parent is the Hydra config dir.
+    """
+    # Hydra needs a path relative to this file.
+    hydra.initialize(
+        str(_relative_path_between(Path(config_path).absolute().parent, Path(__file__).absolute().parent))
+    )
+    cfg = hydra.compose(Path(config_path).stem, overrides)
+    return cfg