scikit-optimize · samuelduchesne · Sep 14, 2021 · Sep 14, 2021 · Oct 1, 2021
diff --git a/skopt/space/transformers.py b/skopt/space/transformers.py
@@ -4,6 +4,7 @@
 from sklearn.utils import column_or_1d
 
 
+
 class Transformer(object):
     """Base class for all 1-D transformers.
     """
@@ -172,8 +173,9 @@ def fit(self, X):
         else:
             i = 0
             self.mapping_ = {}
-            for v in np.unique(X):
-                self.mapping_[v] = i
+            _, indexes = np.unique(X, return_index=True)
+            for index in sorted(indexes):
+                self.mapping_[X[index]] = i
                 i += 1
         self.inverse_mapping_ = {i: v for v, i in self.mapping_.items()}
         return self

diff --git a/skopt/tests/test_space.py b/skopt/tests/test_space.py
@@ -415,7 +415,7 @@ def test_normalize_types():
     # can you pass a Space instance to the Space constructor?
     space = Space([(0.0, 1.0), Integer(-5, 5, dtype=int), (True, False)])
     space.set_transformer("normalize")
-    X = [[0., -5, False]]
+    X = [[0., -5, True]]
     Xt = np.zeros((1, 3))
     assert_array_equal(space.transform(X), Xt)
     assert_array_equal(space.inverse_transform(Xt), X)