pandas fillna方法不适用于原位 [英] Pandas fillna method does not work inplace
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问题描述
我有一个数据框问题数据,在某些单元格中具有NaN值.我运行了以下代码.
I have a dataframe problem_data which has NaN values in some cells. I ran the following code.
problem_data[problem_data['level_type'] == 5.0]
结果是这样:
problem_id level_type points tags
5 prob_1479 5.0 NaN NaN
31 prob_2092 5.0 NaN NaN
38 prob_4395 5.0 NaN combinatorics,constructive algorithms,dfs
43 prob_5653 5.0 NaN NaN
48 prob_2735 5.0 2750.0 NaN
52 prob_1054 5.0 2000.0 combinatorics,dp
64 prob_2610 5.0 NaN NaN
65 prob_1649 5.0 NaN NaN
70 prob_4675 5.0 NaN dp,games
74 prob_445 5.0 NaN NaN
81 prob_6481 5.0 2500.0 combinatorics,dp,implementation,number theory
134 prob_2964 5.0 2500.0 games
161 prob_948 5.0 2000.0 dp,games
182 prob_642 5.0 NaN NaN
然后,我运行以下命令以填充点"列的NaN.
Then, I ran the following command to fill the NaN of 'points' column.
problem_data.loc[problem_data['level_type'] == 5.0 , 'points'].fillna(value=2500, inplace=True)
当我再次运行problem_data[problem_data['level_type'] == 5.0]
时,输出与以前相同.
When, I ran problem_data[problem_data['level_type'] == 5.0]
again, the output was same as before.
您能说出为什么fillna()
在这里不起作用吗?我该怎么做才能纠正它?
Can you tell why fillna()
didn't work here? What can I do to correct it?
推荐答案
fillna
不适用于数据帧子切片.您需要:
fillna
does not work inplace on dataframe sub-slices. You'll want:
mask = problem_data['level_type'] == 5.0
problem_data.loc[mask, 'points'] = problem_data.loc[mask, 'points'].fillna(value=2500)
problem_data.loc[mask, 'points']
5 2500.0
31 2500.0
38 2500.0
43 2500.0
48 2750.0
52 2000.0
64 2500.0
65 2500.0
70 2500.0
74 2500.0
81 2500.0
134 2500.0
161 2000.0
182 2500.0
Name: points, dtype: float64
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