fix: Fix explode invalid check (#17651)

crates/polars-core/src/frame/explode.rs

@@ -83,7 +83,18 @@ impl DataFrame {
         let check_offsets = || {
             let first_offsets = exploded_columns[0].1.as_slice();
             for (_, offsets) in &exploded_columns[1..] {
-                polars_ensure!(first_offsets == offsets.as_slice(),
+                let offsets = offsets.as_slice();
+
+                let offset_l = first_offsets[0];
+                let offset_r = offsets[0];
+                let all_equal_len = first_offsets.len() != offsets.len() || {
+                    first_offsets
+                        .iter()
+                        .zip(offsets.iter())
+                        .all(|(l, r)| (*l - offset_l) == (*r - offset_r))
+                };
+
+                polars_ensure!(all_equal_len,
                     ShapeMismatch: "exploded columns must have matching element counts"
                 )
             }

py-polars/tests/unit/operations/test_explode.py

@@ -438,3 +438,12 @@ def test_undefined_col_15852() -> None:
 
     with pytest.raises(pl.exceptions.ColumnNotFoundError):
         lf.explode("bar").join(lf, on="foo").collect()
+
+
+def test_explode_17648() -> None:
+    df = pl.DataFrame({"a": [[1, 3], [2, 6, 7], [3, 9, 2], [4], [5, 1, 2, 3, 4]]})
+    assert (
+        df.slice(1, 2)
+        .with_columns(pl.int_ranges(pl.col("a").list.len()).alias("count"))
+        .explode("a", "count")
+    ).to_dict(as_series=False) == {"a": [2, 6, 7, 3, 9, 2], "count": [0, 1, 2, 0, 1, 2]}