Append 星号到现有的 dataframe 值，基于与另一个 dataframe 中的 dataframe 的掩码

Question

I have two dataframes:

import pandas as pd
data1 = {1: [1,2,3], 2: [1,2,3]}
df1 = pd.DataFrame(data1)

data2 = {1: [49,60,12], 2: [14,70,38]}
df2 = pd.DataFrame(data2)

Where a value is >= 30 but <50 in df2, I want to append an * to the respective existing value in df1. I tried:

df1 = df1.mask((df2 >= 30) & (df2 < 50), [df1 + '*'])

But this gives an error.

Thanks in advance.

Answer 1

You are close, remove [] and convert values to strings for add * :

df = df1.mask((df2 >= 30) & (df2 < 50), df1.astype(str) + '*')
print (df)
    1   2
0  1*   1
1   2   2
2   3  3*