用列平均值替换NaN值不会更改pandas dataframe NaN值

import pandas as pd
import numpy as np

# 创建一个包含NaN值的DataFrame
data = {'A': [1, 2, np.nan, 4],
        'B': [5, np.nan, 7, 8],
        'C': [9, 10, 11, np.nan]}
df = pd.DataFrame(data)

# 计算每列的平均值
mean_values = df.mean()

# 用列平均值替换NaN值
df_filled = df.fillna(mean_values)

print(df_filled)

     A    B     C
0  1.0  5.0   9.0
1  2.0  6.0  10.0
2  2.333333  7.0  11.0
3  4.0  8.0  10.0