Refactor code

Author: howsiwei

pandas/core/frame.py

@@ -3007,12 +3007,7 @@ def _setitem_array(self, key, value):
                 for k1, k2 in zip(key, value.columns):
                     self[k1] = value[k2]
             else:
-                if all(is_hashable(k) for k in key):
-                    for k in key:
-                        try:
-                            self[k]
-                        except KeyError:
-                            self[k] = np.nan
+                self.loc._ensure_listlike_indexer(key, axis=1)
                 indexer = self.loc._get_listlike_indexer(
                     key, axis=1, raise_missing=False
                 )[1]

pandas/core/indexing.py

@@ -167,7 +167,28 @@ def _get_loc(self, key: int, axis: int):
     def _slice(self, obj, axis: int, kind=None):
         return self.obj._slice(obj, axis=axis, kind=kind)
 
+    def _ensure_listlike_indexer(self, key, axis):
+        # if `key` is an index to multiple columns by name, add each column
+        # if it does not already exist
+        if not isinstance(self.obj._get_axis(axis), ABCMultiIndex) and all(
+            is_hashable(k) for k in key
+        ):
+            for k in key:
+                try:
+                    self.obj[k]
+                except KeyError:
+                    self.obj[k] = np.nan
+
     def _get_setitem_indexer(self, key):
+        if (
+            self.name == "loc"  # column is indexed by name
+            and isinstance(key, tuple)
+            and len(key) >= 2  # key is at least 2-dimensional
+            and is_list_like_indexer(key[1])  # key indexes multiple columns
+            and not com.is_bool_indexer(key[1])
+        ):
+            self._ensure_listlike_indexer(key[1], axis=1)
+
         if self.axis is not None:
             return self._convert_tuple(key)
 
@@ -202,21 +223,6 @@ def _get_setitem_indexer(self, key):
     def __setitem__(self, key, value):
         if isinstance(key, tuple):
             key = tuple(com.apply_if_callable(x, self.obj) for x in key)
-            # if `key` is an index to multiple columns by name, add each column
-            # if it does not already exist
-            if (
-                self.name == "loc"  # column is indexed by name
-                and len(key) >= 2  # key is at least 2-dimensional
-                and is_list_like_indexer(key[1])  # key indexes multiple columns
-                and not isinstance(self.obj._get_axis(1), ABCMultiIndex)
-                and not com.is_bool_indexer(key[1])
-                and all(is_hashable(k) for k in key[1])
-            ):
-                for k in key[1]:
-                    try:
-                        self.obj[k]
-                    except KeyError:
-                        self.obj[k] = np.nan
         else:
             key = com.apply_if_callable(key, self.obj)
         indexer = self._get_setitem_indexer(key)