how to loop adding new column to pandas dataframe with value is based on other column value

Question

Please I have dataframe with four columns that are [keys, summary, description, and summary_description], so iam dealing with summary_description, trying to apply RegEx and extract the new result in a [New_column], so I have done the looping but Iam not sure what is the problem not working getting error. Please if anyone could help, I would really appreciate it.

import pandas as pd
import re
dataf= pd.read_excel(r'C:\Users\malotaibi\Desktop\Last update\result.xlsx')
dataf
dataf.head(5)
dataf['New_Column'][i] = re.sub('[^A-Za-z0-9]+', ' ', dataf['Summary_Description'][i])
print (dataf['New_column'][i])

Error:

KeyError: 'New_Column'

You should do print(dataf.columns), it'll show you the columns you have access to. It says there is no column New_Column with a capital C. Check it again. — IMCoins
– IMCoins, Commented Jul 2, 2019 at 14:00
iam not sure if my loop is correct ot not, but I did what you said print(dataf.columns), is still the same problem, iam using jupyter. thanks — Mofaq
– Mofaq, Commented Jul 2, 2019 at 14:06

SteelFeather · Accepted Answer · 2019-07-02 14:15:18Z

1

You can do it like this:

dataf['New_Column'] = dataf['Summary_Description'].str.replace('[^A-Za-z0-9]+', ' ')

answered Jul 2, 2019 at 14:15

SteelFeather

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Comments

Jamie J · Accepted Answer · 2019-07-02 14:13:48Z

0

You have tried to add to the 'New Column' key before creating it. So do

import pandas as pd
import re
dataf= pd.read_excel(r'C:\Users\malotaibi\Desktop\Last update\result.xlsx')
dataf
dataf.head(5)
dataf['New_Column'] = 1 # this will create the new_column entry and set all its values to 1

You can now loop through this and set each value to what you want. I assume you're going for something like:

for i in range(len(dataf['Summary_Description'])):
    dataf['New_Column'][i] = re.sub('[^A-Za-z0-9]+', ' ', dataf['Summary_Description'][i])

edited Jul 2, 2019 at 14:13

answered Jul 2, 2019 at 14:08

Jamie J

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2 Comments

Mofaq Over a year ago

Thank you so much Kathy for your time, it really helped.

Jamie J Over a year ago

No worries, though I'd like to point out the answer below given by PraveenB is much cleaner and also works, but its up to you

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