我想将单个值添加到 Pandas 数据框中的多行

Question

Okay suppose I have a data frame A

A:

col1 col2
 1    2
 3    4

I am not going to add two more columns to it col3 and col4 and want to populate it like so

col1 col2 col3 col4
 1    2    5    6
 3    4    5    6

All the values of col3 need to be 5 and all the values of col4 need to be 6 no matter the number of rows

is there a way to do this without a loop?

Answer 1

You can add multiple columns with constant values for all rows like below:

In [268]: df
Out[268]: 
   col1  col2
0     1     2
1     3     4

In [269]: df[['col3', 'col4']] = [5,6]

In [270]: df
Out[270]: 
   col1  col2  col3  col4
0     1     2     5     6
1     3     4     5     6

Answer 2

You can simply use assign function:

df = df.assign(
    col3 = 5,
    col4 = 6
)