如何为字典内的GeoDataFrame应用函数并创建'x'字段？

我有一个名为var_holder3的字典，其values是GeoDataFrame，keys是对应GeoDataFrame的变量名。我需要应用getPolyCoords函数，为这些GeoDataFrame创建'x'字段。函数定义如下：

def getPolyCoords(row, geom, coord_type):
     exterior = row[geom].exterior
     if coord_type == 'x':
         return list( exterior.coords.xy[0] )
     elif coord_type == 'y':
         return list( exterior.coords.xy[1] )

我尝试了以下代码：

for x in var_holder3:
    var_holder3[x]['x'].apply(getPolyCoords, geom='geometry', coord_type='x', axis=1)

期望得到带有新字段'x'的GeoDataFrame，但出现KeyError: 'x'错误，错误栈信息如下：

Traceback (most recent call last):
  File "/home/kevin1/anaconda3/lib/python3.9/site-packages/pandas/core/indexes/base.py", line 3803, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas/_libs/index.pyx", line 138, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 165, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 5745, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 5753, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 'x'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/home/kevin1/anaconda3/lib/python3.9/site-packages/geopandas/geodataframe.py", line 1415, in __getitem__
    result = super().__getitem__(key)
  File "/home/kevin1/anaconda3/lib/python3.9/site-packages/pandas/core/frame.py", line 3805, in __getitem__
    indexer = self.columns.get_loc(key)
  File "/home/kevin1/anaconda3/lib/python3.9/site-packages/pandas/core/indexes/base.py", line 3805, in get_loc
    raise KeyError(key) from err
KeyError: 'x'

• 错误原因：代码中提前访问了还未创建的'x'字段（var_holder3[x]['x']），此时该字段不存在，触发KeyError。正确逻辑是先对整个GeoDataFrame调用apply计算结果，再将结果赋值给新的'x'字段。
• 修正后的代码：

for x in var_holder3:
    # 对GeoDataFrame执行apply，将结果赋值给新字段'x'
    var_holder3[x]['x'] = var_holder3[x].apply(getPolyCoords, geom='geometry', coord_type='x', axis=1)

执行后，每个GeoDataFrame都会新增'x'字段，存储对应多边形外部轮廓的x坐标列表。

内容的提问来源于stack exchange，提问作者Peter