Merge pull request #25756 from charris/backport-24711

BUG: Fix np.quantile([Fraction(2,1)], 0.5) (#24711)

numpy/lib/function_base.py

@@ -4655,7 +4655,8 @@ def _lerp(a, b, t, out=None):
     diff_b_a = subtract(b, a)
     # asanyarray is a stop-gap until gh-13105
     lerp_interpolation = asanyarray(add(a, diff_b_a * t, out=out))
-    subtract(b, diff_b_a * (1 - t), out=lerp_interpolation, where=t >= 0.5)
+    subtract(b, diff_b_a * (1 - t), out=lerp_interpolation, where=t >= 0.5,
+             casting='unsafe', dtype=type(lerp_interpolation.dtype))
     if lerp_interpolation.ndim == 0 and out is None:
         lerp_interpolation = lerp_interpolation[()]  # unpack 0d arrays
     return lerp_interpolation

numpy/lib/tests/test_function_base.py

@@ -3606,6 +3606,10 @@ def test_fraction(self):
         assert_equal(q, Fraction(7, 2))
         assert_equal(type(q), Fraction)
 
+        q = np.quantile(x, .5)
+        assert_equal(q, 1.75)
+        assert_equal(type(q), np.float64)
+
         q = np.quantile(x, Fraction(1, 2))
         assert_equal(q, Fraction(7, 4))
         assert_equal(type(q), Fraction)