如何在for循环内的pandas数据框中创建其他列

Question

I am working with pandas and would like to add columns to my dataframe from a list. Ideally I would like to iterate through my list in a for loop creating a single column in each pass.

Example:

import pandas as pd

d = {
'name':['Ken','Bobby'],
'age':[5,6],
'score':[1,2]}

df = pd.DataFrame(d,columns=['name','age','score'])

new_columns = ['col1', 'col2']

Output:

    name    age     score
    Ken     5       1
    Bobby   6       2

Desired output:

    name    age     score   col1     col2
    Ken     5       1       1        1
    Bobby   6       2       2        2

Corrected solution:

for i in new_columns:
     df[i] = pd.Series([1,2])

Edit:

I have corrected the code to fix a typo however there is a great additional solution that does not use for loops which I intend to use in the future.

Answer 1

One way of doing that without for loop , assign

df=df.assign(**dict.fromkeys(new_columns,[1,2]))
df
Out[84]: 
    name  age  score  col1  col2
0    Ken    5      1     1     1
1  Bobby    6      2     2     2

Also you do not need Series when creating the new columns

for i in new_columns:
     df[i] = [1,2]

df
Out[86]: 
    name  age  score  col1  col2
0    Ken    5      1     1     1
1  Bobby    6      2     2     2

---

Notice , Personally not recommend using Series to assign , since pandas is index sensitive , which means when your dataframe index is not from range 0 - n , the assign will fail. For example

df.index=[100,101]
for i in new_columns:
     df[i] = pd.Series([1,2])

df
Out[89]: 
      name  age  score  col1  col2
100    Ken    5      1   NaN   NaN
101  Bobby    6      2   NaN   NaN