feat: Add support for path in map fn

src/litdata/processing/functions.py

@@ -207,8 +207,8 @@ def prepare_item(self, item_metadata: Any) -> Any:
 def map(
     fn: Callable[[str, Any], None],
     inputs: Union[Sequence[Any], StreamingDataLoader],
-    output_dir: Union[str, Dir],
-    input_dir: Optional[str] = None,
+    output_dir: Union[str, Path, Dir],
+    input_dir: Optional[Union[str, Path]] = None,
     weights: Optional[List[int]] = None,
     num_workers: Optional[int] = None,
     fast_dev_run: Union[bool, int] = False,

src/litdata/streaming/resolver.py

@@ -38,28 +38,28 @@ class Dir:
     url: Optional[str] = None
 
 
-def _resolve_dir(dir_path: Optional[Union[str, Dir]]) -> Dir:
+def _resolve_dir(dir_path: Optional[Union[str, Path, Dir]]) -> Dir:
     if isinstance(dir_path, Dir):
         return Dir(path=str(dir_path.path) if dir_path.path else None, url=str(dir_path.url) if dir_path.url else None)
 
     if dir_path is None:
         return Dir()
 
-    if not isinstance(dir_path, str):
-        raise ValueError(f"`dir_path` must be a `Dir` or a string, got: {dir_path}")
+    if not isinstance(dir_path, (str, Path)):
+        raise ValueError(f"`dir_path` must be either a string, Path, or Dir, got: {dir_path}")
 
-    assert isinstance(dir_path, str)
+    if isinstance(dir_path, str):
+        cloud_prefixes = ("s3://", "gs://", "azure://", "hf://")
+        if dir_path.startswith(cloud_prefixes):
+            return Dir(path=None, url=dir_path)
 
-    cloud_prefixes = ("s3://", "gs://", "azure://", "hf://")
-    if dir_path.startswith(cloud_prefixes):
-        return Dir(path=None, url=dir_path)
+        if dir_path.startswith("local:"):
+            return Dir(path=None, url=dir_path)
 
-    if dir_path.startswith("local:"):
-        return Dir(path=None, url=dir_path)
-
-    dir_path = _resolve_time_template(dir_path)
+        dir_path = _resolve_time_template(dir_path)
 
     dir_path_absolute = str(Path(dir_path).absolute().resolve())
+    dir_path = str(dir_path)  # Convert to string if it was a Path object
 
     if dir_path_absolute.startswith("/teamspace/studios/this_studio"):
         return Dir(path=dir_path_absolute, url=None)
@@ -345,7 +345,22 @@ def _get_lightning_cloud_url() -> str:
 
 
 def _resolve_time_template(path: str) -> str:
-    match = re.search("^.*{%.*}$", path)
+    """Resolves a datetime pattern in the given path string.
+
+    If the path contains a placeholder in the form `{%Y-%m-%d}`, it replaces it
+    with the current date/time formatted using the specified `strftime` pattern.
+
+    Example:
+        Input: "/logs/log_{%Y-%m-%d}.txt"
+        Output (on May 5, 2025): "/logs/log_2025-05-05.txt"
+
+    Args:
+        path (str): The file path containing an optional datetime placeholder.
+
+    Returns:
+        str: The path with the datetime placeholder replaced by the current timestamp.
+    """
+    match = re.search("^.*{%.*}.*$", path)
     if match is None:
         return path
 

tests/processing/test_functions.py

@@ -14,7 +14,7 @@
 import torch
 from PIL import Image
 
-from litdata import StreamingDataset, merge_datasets, optimize, walk
+from litdata import StreamingDataset, map, merge_datasets, optimize, walk
 from litdata.processing.functions import _get_input_dir, _resolve_dir
 from litdata.streaming.cache import Cache
 from litdata.utilities.encryption import FernetEncryption, RSAEncryption
@@ -58,6 +58,44 @@ def test_get_input_dir_with_s3_path():
     assert input_dir.url == "s3://my_bucket/my_folder"
 
 
+def update_msg(file_path: Path, output_dir: Path):
+    with open(os.path.join(output_dir, file_path.name), "w") as f:
+        f.write("Bonjour!")
+
+
+def test_map_with_path(tmpdir):
+    input_dir = Path(tmpdir) / "input_dir"
+    output_dir = Path(tmpdir) / "output_dir"
+
+    os.makedirs(input_dir, exist_ok=True)
+    os.makedirs(output_dir, exist_ok=True)
+
+    for i in range(5):
+        filepath = os.path.join(input_dir, f"{i}.txt")
+        with open(filepath, "w") as f:
+            f.write("hello world!")
+
+    # read all files in the input directory, and assert it contains hello world!
+    for file in input_dir.iterdir():
+        with open(file) as f:
+            content = f.read()
+            assert content == "hello world!"
+
+    inputs = list(input_dir.iterdir())  # List all files in the directory
+
+    map(
+        fn=update_msg,
+        inputs=inputs,
+        output_dir=output_dir,
+    )
+
+    # read all files in the output directory, and assert it contains Bonjour!
+    for file in output_dir.iterdir():
+        with open(file) as f:
+            content = f.read()
+            assert content == "Bonjour!"
+
+
 def compress(index):
     return index, index**2
 

tests/streaming/test_resolver.py

@@ -1,3 +1,4 @@
+import datetime
 import sys
 from pathlib import Path
 from unittest import mock
@@ -388,3 +389,17 @@ def test_resolve_dir_absolute(tmp_path, monkeypatch):
     link.symlink_to(src)
     assert link.resolve() == src
     assert resolver._resolve_dir(str(link)).path == str(src)
+
+
+def test_resolve_time_template():
+    path_1 = "/logs/log_{%Y-%m}"
+    path_2 = "/logs/my_logfile"
+    path_3 = "/logs/log_{%Y-%m}/important"
+
+    current_datetime = datetime.datetime.now()
+    curr_year = current_datetime.year
+    curr_month = current_datetime.month
+
+    assert resolver._resolve_time_template(path_1) == f"/logs/log_{curr_year}-{curr_month:02d}"
+    assert resolver._resolve_time_template(path_2) == path_2
+    assert resolver._resolve_time_template(path_3) == f"/logs/log_{curr_year}-{curr_month:02d}/important"