Python - loop column names

Question

I can't find solution to my problem. I have dataframe like

import pandas as pd
df = pd.DataFrame({'A':[4,5,4,5,5,4],
                   'B':[7,8,9,4,2,3],
                   'C':[1,3,5,7,1,0]})

I'd like to make 5 new columns B_1, B_2, ..., B_5 in which i would like define cells based on function x-i, where x is cell value and i is iteration step (1,..,5) - it would be enough to have desired result for column B. B_1 should be [6,7,8,3,1,2] etc.. Can you please give me some hints?

Thanks

yeah, but would be glad to see solution using loop. I need it for larger and more complicated data sets. — Matlas
– Matlas, Commented Apr 19, 2020 at 18:53
it would be helpful if u provide ur expected output, just as u posted an input dataframe. — sammywemmy
– sammywemmy, Commented Apr 19, 2020 at 22:25

gosuto · Accepted Answer · 2020-04-19 18:54:16Z

1

In the case of having five iterations, and them being known in advance:

for col in df.columns:
    for i in range(1, 6):
        df[f'{col}_{i}'] = df[col] - i

answered Apr 19, 2020 at 18:54

gosuto

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7 Comments

Matlas Over a year ago

thanks, works really good, but something is wrong when my column name have more than one letter in name; do you know what's happening? for example for name 'Age' instead of 'A'

gosuto Over a year ago

Shouldn't matter. df.columns is a list of strings, whether it contains 'A' or 'Age' is indifferent to the rest of the code.

Matlas Over a year ago

I changed column name 'A' for 'Age' and tried to do the same thing just for this column, but this time some error is happening ` for col in df.columns[0]: for i in range(1, 6): df[f'{col}_{i}'] = df[col] - i`

gosuto Over a year ago

Why did you add [0]?

gosuto Over a year ago

The it's going to loop through the string letter by letter. If you only want it for a certain column just col = 'A' and get rid of the first for loop.

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