Pandas DataFrame-根据条件进行修改

Question

我有这个数据框

import pandas as pd
x = pd.DataFrame.from_dict({'A':[1,2,0,4,0,6], 'B':[0, 0, 0, 44, 48, 81], 'C':[1,0,1,0,1,0]})

我尝试像这样更改它，但不起作用

x[x['A']>3]['A'] = 33 # has no effect

我也尝试过

x.loc(x['A']>3)['A'] = 33 # getting an error

那么正确的方法是什么？

Answer 1

您应该使用.loc

x.loc[x['A']>3,'A'] = 33
x
Out[480]: 
    A   B  C
0   1   0  1
1   2   0  0
2   0   0  1
3  33  44  0
4   0  48  1
5  33  81  0

或mask

x.A=x.mask(x.A>3,33)
x
Out[483]: 
    A   B  C
0   1   0  1
1   2   0  0
2   0   0  1
3  33  44  0
4   0  48  1
5  33  81  0