ValueError:fillvaluemustbeincategories.

执行下面代码时报错&＃xff1a;ValueError: fill value must be in categories

import pandas as pd;
import numpy as np;df &＃61; pd.DataFrame({&＃39;a&＃39;:[1, 2, 3, 4], &＃39;b&＃39;:[&＃39;d&＃39;, &＃39;e&＃39;, &＃39;f&＃39;, None]}, dtype&＃61;&＃39;category&＃39;);
print(df)df[&＃39;b&＃39;].fillna(&＃39;k&＃39;, inplace&＃61;True);
print(df)


修正&＃xff1a;

import pandas as pd;
import numpy as np;df &＃61; pd.DataFrame({&＃39;a&＃39;:[1, 2, 3, 4], &＃39;b&＃39;:[&＃39;d&＃39;, &＃39;e&＃39;, &＃39;f&＃39;, None]}, dtype&＃61;&＃39;category&＃39;);
print(df)df[&＃39;b&＃39;] &＃61; df[&＃39;b&＃39;].cat.add_categories([&＃39;k&＃39;]);
df[&＃39;b&＃39;].fillna(&＃39;k&＃39;, inplace&＃61;True);
print(df)

原因&＃xff1a;
对于数据类型为category的“b”&＃xff0c;fillna函数所填充的值需要已经存在于‘b’中。这句话df[&＃39;b&＃39;] &＃61; df[&＃39;b&＃39;].cat.add_categories([&＃39;k&＃39;]);表示在’b’列中新添一个类别k。

结束&＃xff01;