python - 类型错误 : 'fill_value= xx ' is not present in this Categorical's categories

Question

我使用 groupby 和 unstack 创建一个数据框，并希望为订阅率创建一个新列。

df_sub = df.groupby(['time_section', 'day_type', 'user_type']).size().unstack()
df_sub['ratio'] = df_sub['Subscriber'] / df_sub['Customer']

结果出现错误“TypeError: 'fill_value=ratio' 不存在于此分类的类别中”

有人可以帮助我吗？

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
   3079             try:
-> 3080                 return self._engine.get_loc(casted_key)
   3081             except KeyError as err:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 'ratio'

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

KeyError                                  Traceback (most recent call last)
/opt/anaconda3/lib/python3.8/site-packages/pandas/core/generic.py in _set_item(self, key, value)
   3825         try:
-> 3826             loc = self._info_axis.get_loc(key)
   3827         except KeyError:

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
   3077                 )
-> 3078             casted_key = self._maybe_cast_indexer(key)
   3079             try:

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/category.py in _maybe_cast_indexer(self, key)
    495     def _maybe_cast_indexer(self, key) -> int:
--> 496         return self._data._unbox_scalar(key)
    497 

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/arrays/categorical.py in _unbox_scalar(self, key)
   1720         # to same dtype as self.codes, we get much faster performance.
-> 1721         code = self.categories.get_loc(key)
   1722         code = self._codes.dtype.type(code)

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
   3081             except KeyError as err:
-> 3082                 raise KeyError(key) from err
   3083 

KeyError: 'ratio'

During handling of the above exception, another exception occurred:

TypeError                                 Traceback (most recent call last)
<ipython-input-80-ef99a6bd1acd> in <module>
----> 1 df_sub['ratio'] = df_sub['Subscriber'] / df_sub['Customer']

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/frame.py in __setitem__(self, key, value)
   3161         else:
   3162             # set column
-> 3163             self._set_item(key, value)
   3164 
   3165     def _setitem_slice(self, key: slice, value):

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/frame.py in _set_item(self, key, value)
   3241         self._ensure_valid_index(value)
   3242         value = self._sanitize_column(key, value)
-> 3243         NDFrame._set_item(self, key, value)
   3244 
   3245         # check if we are modifying a copy

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/generic.py in _set_item(self, key, value)
   3827         except KeyError:
   3828             # This item wasn't present, just insert at end
-> 3829             self._mgr.insert(len(self._info_axis), key, value)
   3830             return
   3831 

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/internals/managers.py in insert(self, loc, item, value, allow_duplicates)
   1195 
   1196         # insert to the axis; this could possibly raise a TypeError
-> 1197         new_axis = self.items.insert(loc, item)
   1198 
   1199         if value.ndim == self.ndim - 1 and not is_extension_array_dtype(value.dtype):

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/extension.py in insert(self, loc, item)
    377         """
    378         arr = self._data
--> 379         code = arr._validate_scalar(item)
    380 
    381         new_vals = np.concatenate((arr._ndarray[:loc], [code], arr._ndarray[loc:]))

/opt/anaconda3/lib/python3.8/site-packages/pandas/core/arrays/categorical.py in _validate_fill_value(self, fill_value)
   1249             fill_value = self._unbox_scalar(fill_value)
   1250         else:
-> 1251             raise TypeError(
   1252                 f"'fill_value={fill_value}' is not present "
   1253                 "in this Categorical's categories"

TypeError: 'fill_value=ratio' is not present in this Categorical's categories

data frame

df_sub.index
MultiIndex([('10am-12pm', 'weekday'),
            ('10am-12pm', 'weekend'),
            ('10pm-12am', 'weekday'),
            ('10pm-12am', 'weekend'),
            (  '1am-3am', 'weekday'),
            (  '1am-3am', 'weekend'),
            (  '1pm-3pm', 'weekday'),
            (  '1pm-3pm', 'weekend'),
            (  '4am-6am', 'weekday'),
            (  '4am-6am', 'weekend'),
            (  '4pm-6pm', 'weekday'),
            (  '4pm-6pm', 'weekend'),
            (  '7am-9am', 'weekday'),
            (  '7am-9am', 'weekend'),
            (  '7pm-9pm', 'weekday'),
            (  '7pm-9pm', 'weekend')],
           names=['time_section', 'day_type'])
df_sub.columns
CategoricalIndex(['Customer', 'Subscriber'], categories=['Customer', 'Subscriber'], ordered=False, name='user_type', dtype='category')

Answer 1

使用CategoricalIndex.add_categories对于 CategoricalIndex 中的新类别:

df_sub = df.groupby(['time_section', 'day_type', 'user_type']).size().unstack()
df_sub.columns = df_sub.columns.add_categories(['ratio'])
df_sub['ratio'] = df_sub['Subscriber'] / df_sub['Customer']