implemented the searchsorted() method, w.r.t issue pandas-dev#18433

Author: GSAUC3

pandas/core/indexes/multi.py

@@ -3814,22 +3814,37 @@ def searchsorted(
         >>> mi.searchsorted(("b", "y"))
         1
         """
-        if isinstance(value, tuple):
-            value = list(value)
+        if not isinstance(value, (tuple,list)):   
+            raise TypeError("value must be a tuple or list")
 
+        if isinstance(value, tuple):
+            value = [value]
         if side not in ["left", "right"]:
             raise ValueError("side must be either 'left' or 'right'")
 
         if not value:
             raise ValueError("searchsorted requires a non-empty value")
 
-        
-
-        dtype = np.dtype([(f"level_{i}", level.dtype) for i,level in enumerate(self.levels)])
- 
-        val = np.asarray(value, dtype=dtype)
-
-        return np.searchsorted(self.values.astype(dtype),val, side=side, sorter=sorter) 
+        try: 
+  
+            indexer = self.get_indexer(value)
+            result = []
+
+            for v, i in zip(value, indexer):
+                if i!= -1:
+                    result.append(i if side == "left" else i + 1)
+                else: 
+                    dtype = np.dtype([(f"level_{i}", level.dtype) for i, level in enumerate(self.levels)])
+
+                    val_array = np.array(value, dtype=dtype)
+                    
+                    pos = np.searchsorted( np.asarray(self.values,dtype=dtype),val_array , side=side, sorter = sorter)
+                    result.append(pos)
+            
+            return np.array(result, dtype=np.intp)
+
+        except KeyError:
+            pass
 
 
     def truncate(self, before=None, after=None) -> MultiIndex:

pandas/tests/indexes/multi/test_indexing.py

@@ -1029,3 +1029,40 @@ def test_get_loc_namedtuple_behaves_like_tuple():
         assert idx.get_loc(("i1", "i2")) == 0
         assert idx.get_loc(("i3", "i4")) == 1
         assert idx.get_loc(("i5", "i6")) == 2
+
+
+
+
+def test_searchsorted():
+    mi = MultiIndex.from_tuples([
+        ('a', 0),
+        ('a', 1),
+        ('b', 0),
+        ('b', 1),
+        ('c', 0)
+    ])
+
+    
+    assert mi.searchsorted(('b', 0)) == 2
+    assert mi.searchsorted(('b', 0), side="right") == 3
+    
+    assert mi.searchsorted(('a', 0)) == 0
+    assert mi.searchsorted(('a', -1)) == 0
+    assert mi.searchsorted(('c', 1)) == 5  # Beyond the last
+
+    
+    result = mi.searchsorted([('a', 1), ('b', 0), ('c', 0)])
+    expected = np.array([1, 2, 4], dtype=np.intp)
+    np.testing.assert_array_equal(result, expected)
+
+    
+    result = mi.searchsorted([('a', 1), ('b', 0), ('c', 0)], side='right')
+    expected = np.array([2, 3, 5], dtype=np.intp)
+    np.testing.assert_array_equal(result, expected)
+
+    
+    with pytest.raises(ValueError, match="side must be either 'left' or 'right'"):
+        mi.searchsorted(('a', 1), side='middle')
+ 
+    with pytest.raises(TypeError, match="value must be a tuple or list"):
+        mi.searchsorted('a')  # not a tuple