Pandas fillna 抛出 ValueError：填充值必须在类别中
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Pandas fillna throws ValueError: fill value must be in categories
提问by Ravi Varma
Discription: both features are in categorical dtypes. and i used this code in a different kernal of same dateset was working fine, the only difference is the features are in flote64. later i have converted these feature dtypes into Categorical because all the features in the dataset represents categories.
描述：这两个特征都在分类 dtypes 中。我在相同日期集的不同内核中使用此代码工作正常，唯一的区别是功能在 flote64 中。后来我将这些特征 dtype 转换为 Categorical，因为数据集中的所有特征都代表类别。
Below is the code:
下面是代码：
AM_train['product_category_2'].fillna('Unknown', inplace =True)
AM_train['city_development_index'].fillna('Missing', inplace =True)
回答by jezrael
Use Series.cat.add_categoriesfor add categories first:
使用Series.cat.add_categories了添加类别第一：
AM_train['product_category_2'] = AM_train['product_category_2'].cat.add_categories('Unknown')
AM_train['product_category_2'].fillna('Unknown', inplace =True)
AM_train['city_development_index'] = AM_train['city_development_index'].cat.add_categories('Missing')
AM_train['city_development_index'].fillna('Missing', inplace =True)
Sample:
样品：
AM_train = pd.DataFrame({'product_category_2': pd.Categorical(['a','b',np.nan])})
AM_train['product_category_2'] = AM_train['product_category_2'].cat.add_categories('Unknown')
AM_train['product_category_2'].fillna('Unknown', inplace =True)
print (AM_train)
product_category_2
0 a
1 b
2 Unknown
