Capture compression and open binary if present. (#419)

* Capture compression and open binary if present.

* Add non-utf8 encoded test

src/hats/io/file_io/file_io.py

@@ -107,18 +107,19 @@ def load_csv_to_pandas(file_pointer: str | Path | UPath, **kwargs) -> pd.DataFra
 
 
 def load_csv_to_pandas_generator(
-    file_pointer: str | Path | UPath, chunksize=10_000, **kwargs
+    file_pointer: str | Path | UPath, *, chunksize=10_000, compression=None, **kwargs
 ) -> Generator[pd.DataFrame]:
     """Load a csv file to a pandas dataframe
     Args:
         file_pointer: location of csv file to load
-        file_system: fsspec or pyarrow filesystem, default None
+        chunksize (int): number of rows to load per chunk
+        compression (str): for compressed CSVs, the manner of compression. e.g. 'gz', 'bzip'.
         **kwargs: arguments to pass to pandas `read_csv` loading method
     Returns:
         pandas dataframe loaded from CSV
     """
     file_pointer = get_upath(file_pointer)
-    with file_pointer.open("r", **kwargs) as csv_file:
+    with file_pointer.open(mode="rb", compression=compression, **kwargs) as csv_file:
         with pd.read_csv(csv_file, chunksize=chunksize, **kwargs) as reader:
             yield from reader
 

tests/hats/io/file_io/test_file_io.py

@@ -91,6 +91,17 @@ def test_load_csv_to_pandas_generator(small_sky_source_dir):
     assert num_reads == 2
 
 
+def test_load_csv_to_pandas_generator_encoding(tmp_path):
+    path = tmp_path / "koi8-r.csv"
+    with path.open(encoding="koi8-r", mode="w") as fh:
+        fh.write("col1,col2\nыыы,яяя\n")
+    num_reads = 0
+    for frame in load_csv_to_pandas_generator(path, chunksize=7, encoding="koi8-r"):
+        assert len(frame) == 1
+        num_reads += 1
+    assert num_reads == 1
+
+
 def test_write_df_to_csv(tmp_path):
     random_df = pd.DataFrame(np.random.randint(0, 100, size=(100, 4)), columns=list("ABCD"))
     test_file_path = tmp_path / "test.csv"