BUG: np.in1d bug on the object array (issue 17923)

1 files changed, 20 insertions, 4 deletions

diff --git a/numpy/lib/arraysetops.py b/numpy/lib/arraysetops.py
index 6c6c1ff80..e7f9add20 100644
--- a/numpy/lib/arraysetops.py
+++ b/numpy/lib/arraysetops.py
@@ -575,12 +575,28 @@ def in1d(ar1, ar2, assume_unique=False, invert=False):
     if len(ar2) < 10 * len(ar1) ** 0.145 or contains_object:
         if invert:
             mask = np.ones(len(ar1), dtype=bool)
-            for a in ar2:
-                mask &= (ar1 != a)
+            # If ar2.dtype is object, store is used to wrap the a value
+            # in an array to prevent tuples from being unpacked before the comparison
+            if ar2.dtype == object:
+                store = np.empty(shape=1, dtype=object)
+                for a in ar2:
+                    store[0] = a
+                    mask &= (ar1 != store)
+            else:
+                for a in ar2:
+                    mask &= (ar1 != a)
         else:
             mask = np.zeros(len(ar1), dtype=bool)
-            for a in ar2:
-                mask |= (ar1 == a)
+            # If ar2.dtype is object, store is used to wrap the a value
+            # in an array to prevent tuples from being unpacked before the comparison
+            if ar2.dtype == object:
+                store = np.empty(shape=1, dtype=object)
+                for a in ar2:
+                    store[0] = a
+                    mask |= (ar1 == store)
+            else:
+                for a in ar2:
+                    mask |= (ar1 == a)
         return mask
 
     # Otherwise use sorting