Fix issue when subsetting empty GenomicRanges[List] (#59).

src/genomicranges/GenomicRanges.py

@@ -946,6 +946,9 @@ def get_subset(self, subset: Union[str, int, bool, Sequence]) -> "GenomicRanges"
         Returns:
             A new ``GenomicRanges`` object with the ranges of interest.
         """
+        if len(self) == 0:
+            return GenomicRanges.empty()
+
         idx, _ = ut.normalize_subscript(subset, len(self), self._names)
 
         current_class_const = type(self)

src/genomicranges/GenomicRangesList.py

@@ -275,7 +275,13 @@ def __str__(self) -> str:
         output = (
             f"GenomicRangesList with {len(self)} range{'s' if len(self) != 1 else ''}"
         )
-        output += f" and {len(self._mcols)} metadata column{'s' if len(self._mcols) != 1 else ''}\n \n"
+        output += f" and {len(self._mcols)} metadata column{'s' if len(self._mcols) != 1 else ''}\n"
+
+        if isinstance(self._ranges, GenomicRanges) and len(self._ranges) == 0:
+            output += "--- empty genomic ranges list ---"
+            return output
+
+        output += " \n"
 
         nr = len(self)
         added_table = False

tests/test_grl_methods.py

@@ -129,3 +129,7 @@ def test_empty_grl_slice():
     subset = grl[0:10]
     assert isinstance(subset, GenomicRangesList)
     assert len(subset) == 10
+
+    subset = grl[[1, 2, 3]]
+    assert isinstance(subset, GenomicRangesList)
+    assert len(subset) == 3