Move checks to seperate elif

Author: keechongtan

pandas/core/internals/blocks.py

@@ -864,7 +864,11 @@ def setitem(self, indexer, value):
 
         # length checking
         check_setitem_lengths(indexer, value, values)
-
+        exact_match = (
+            len(arr_value.shape)
+            and arr_value.shape[0] == values.shape[0]
+            and arr_value.size == values.size
+        )
         if is_empty_indexer(indexer, arr_value):
             # GH#8669 empty indexers
             pass
@@ -874,21 +878,20 @@ def setitem(self, indexer, value):
             #  be e.g. a list; see GH#6043
             values[indexer] = value
 
-        # if we are an exact match (ex-broadcasting),
-        # then use the resultant dtype
         elif (
-            len(arr_value.shape)
-            and arr_value.shape[0] == values.shape[0]
-            and arr_value.size == values.size
+            self.is_categorical_astype(arr_value.dtype)
+            and not is_categorical_dtype(values)
+            and exact_match
         ):
+            # GH25495 - If the current dtype is not categorical,
+            # we need to create a new categorical block
             values[indexer] = value
+            return self.make_block(Categorical(self.values, dtype=arr_value.dtype))
 
-            if self.is_categorical_astype(arr_value.dtype) and not is_categorical_dtype(
-                values
-            ):
-                # GH25495 - If the current dtype is not categorical,
-                # we need to create a new categorical block
-                return self.make_block(Categorical(self.values, dtype=arr_value.dtype))
+        # if we are an exact match (ex-broadcasting),
+        # then use the resultant dtype
+        elif exact_match:
+            values[indexer] = value
 
             try:
                 values = values.astype(arr_value.dtype)