Move empty df test to py-polars and use concise empty IdxCa new

crates/polars-core/src/chunked_array/random.rs

@@ -10,7 +10,7 @@ use crate::utils::{CustomIterTools, NoNull};
 
 fn create_rand_index_with_replacement(n: usize, len: usize, seed: Option<u64>) -> IdxCa {
     if len == 0 {
-        return NoNull::<IdxCa>::from_iter(std::iter::empty()).into_inner();
+        return IdxCa::new_vec("", vec![]);
     }
     let mut rng = SmallRng::seed_from_u64(seed.unwrap_or_else(get_global_random_u64));
     let dist = Uniform::new(0, len as IdxSize);
@@ -260,22 +260,6 @@ impl BooleanChunked {
 mod test {
     use super::*;
 
-    #[test]
-    fn test_sample_empty_df() {
-        let df = df![
-            "foo" => Vec::<i32>::new()
-        ]
-        .unwrap();
-
-        // If with replacement, then expect empty df
-        assert_eq!(df.sample_n(3, true, false, None).unwrap().height(), 0);
-        assert_eq!(df.sample_frac(0.4, true, false, None).unwrap().height(), 0);
-
-        // If without replacement, then expect shape mismatch on sample_n not sample_frac
-        assert!(df.sample_n(3, false, false, None).is_err());
-        assert_eq!(df.sample_frac(0.4, false, false, None).unwrap().height(), 0);
-    }
-
     #[test]
     fn test_sample() {
         let df = df![

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

@@ -53,6 +53,18 @@ def test_sample_df() -> None:
     assert df.sample(n=2, seed=0).shape == (2, 3)
     assert df.sample(fraction=0.4, seed=0).shape == (1, 3)
 
+def test_sample_empty_df() -> None:
+    df = pl.DataFrame({"foo": []})
+
+    # // If with replacement, then expect empty df
+    assert df.sample(n=3, with_replacement=True).shape == (0, 1)
+    assert df.sample(fraction=0.4, with_replacement=True).shape == (0, 1)
+
+    # // If without replacement, then expect shape mismatch on sample_n not sample_frac
+    with pytest.raises(pl.ShapeError):
+        df.sample(n=3, with_replacement=False)
+    assert df.sample(fraction=0.4, with_replacement=False).shape == (0, 1)
+
 
 def test_sample_series() -> None:
     s = pl.Series("a", [1, 2, 3, 4, 5])