python - 根据条件和年份标记 NaN 值

Question

我试图满足根据条件和特定年份标记 NaN 值的要求，下面是我的代码:

import pandas as pd
import numpy as np
s={'Fruits':['Apple','Orange', 'Banana', 'Mango'],'month':['201401','201502','201603','201604'],'weight':[2,4,1,6],'Quant':[251,178,298,300]}
p=pd.DataFrame(data=s)
upper = 250

如果 upper>250。基本上我的目的是检查 Quant 值是否大于定义的 upper 值，但针对特定日期，即 201603 和 201604。

输出应该是这样的-

Fruits  month   weight  Quant
0   Apple   201401  2   251.0
1   Orange  201502  4   178.0
2   Banana  201603  1   NaN
3   Mango   201604  6   NaN

Answer 1

你可以使用.loc:

p.loc[(p.Quant > upper) & (p.month.str[-2:].isin(['03','04'])), 'Quant'] = np.nan

输出:

   Fruits   month  weight  Quant
0   Apple  201401       2  251.0
1  Orange  201502       4  178.0
2  Banana  201603       1    NaN
3   Mango  201604       6    NaN