python - 你如何在第一行第一列中输入 NaN 值？

Question

import pandas as pd
data=['a',2,],['b',4,1],['c',6,],['d',4.4,]
df = pd.DataFrame(data, columns = ['Name', 'Age','number'])
df
    Name    Age     number
0   a   2.0     NaN
1   b   4.0     1.0
2   c   6.0     NaN
3   d   4.4     NaN

我想用 NaN 值替换“a”(第一行第一列)

出现这个错误

data=[,2,],['b',4,1],['c',6,],['d',4.4,]
      ^
SyntaxError: invalid syntax

我试过这个

data=['',2,],['b',4,1],['c',6,],['d',4.4,]
df = pd.DataFrame(data, columns = ['Name', 'Age','number'])
df

    Name    Age     number
0       2.0     NaN
1   b   4.0     1.0
2   c   6.0     NaN
3   d   4.4     NaN

然后我检查了缺失值，显然它没有在第 1 行第 1 列中提取空值

na= [features for features in df.columns if df[features].isnull().sum()>0]
na

['number']

有关如何解决此问题的任何建议。谢谢你

Answer 1

Pandas 是用 numpy 构建的，所以只需使用 np.nan:

import numpy as np

data=[np.nan,2,],['b',4,1],['c',6,],['d',4.4,]
df = pd.DataFrame(data, columns = ['Name', 'Age','number'])
print (df)

输出:

  Name  Age  number
0  NaN  2.0     NaN
1    b  4.0     1.0
2    c  6.0     NaN
3    d  4.4     NaN