fix: Infer decimal scales on mixed scale input (#17840)

pola-rs · Jul 24, 2024 · 954538e · 954538e
1 parent e96dd26
commit 954538e
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Showing 3 changed files with 19 additions and 3 deletions.
diff --git a/crates/polars-core/src/series/any_value.rs b/crates/polars-core/src/series/any_value.rs
@@ -68,7 +68,7 @@ impl Series {
 
         // TODO: Remove this when Decimal data type equality is implemented.
         #[cfg(feature = "dtype-decimal")]
-        if !strict && dtype.is_decimal() {
+        if dtype.is_decimal() {
             let dtype = DataType::Decimal(None, None);
             return Self::from_any_values_and_dtype(name, values, &dtype, strict);
         }
@@ -488,7 +488,17 @@ fn any_values_to_decimal(
     let mut builder = PrimitiveChunkedBuilder::<Int128Type>::new("", values.len());
     for av in values {
         match av {
-            AnyValue::Decimal(v, s) if *s == scale => builder.append_value(*v),
+            // Allow equal or less scale. We do want to support different scales even in 'strict' mode.
+            AnyValue::Decimal(v, s) if *s <= scale => {
+                if *s == scale {
+                    builder.append_value(*v)
+                } else {
+                    match av.strict_cast(&target_dtype) {
+                        Some(AnyValue::Decimal(i, _)) => builder.append_value(i),
+                        _ => builder.append_null(),
+                    }
+                }
+            },
             AnyValue::Null => builder.append_null(),
             av => {
                 if strict {

diff --git a/py-polars/tests/unit/constructors/test_any_value_fallbacks.py b/py-polars/tests/unit/constructors/test_any_value_fallbacks.py
@@ -299,7 +299,6 @@ def test_fallback_without_dtype(
         [timedelta(hours=0), 1_000],
         [D("12.345"), 100],
         [D("12.345"), 3.14],
-        [D("0.12345"), D("6789.0")],
         [{"a": 1, "b": "foo"}, {"a": -1, "b": date(2020, 12, 31)}],
         [{"a": None}, {"a": 1.0}, {"a": 1}],
     ],

diff --git a/py-polars/tests/unit/datatypes/test_decimal.py b/py-polars/tests/unit/datatypes/test_decimal.py
@@ -515,3 +515,10 @@ def test_decimal_dynamic_float_st() -> None:
     assert pl.LazyFrame({"a": [D("2.0"), D("0.5")]}).filter(
         pl.col("a").is_between(0.45, 0.9)
     ).collect().to_dict(as_series=False) == {"a": [D("0.5")]}
+
+
+def test_decimal_strict_scale_inference_17770() -> None:
+    values = [D("0.1"), D("0.10"), D("1.0121")]
+    s = pl.Series(values, strict=True)
+    assert s.dtype == pl.Decimal(precision=None, scale=4)
+    assert s.to_list() == values