Adding column(s) from one dataframe to another python pandas

Question

I have been searching online and found similar questions but still couldn't find the answer to what I'm looking for. I have 2 excel files:

data1

ColumnA columnB columnC columnD A B C D A B C D A B C D

data2

ColumnE columnF columnG E F G E F G E F G

I want to add the column F from data2 to data1:

ColumnA columnB columnC columnD columnF A B C D F A B C D F A B C D F

I tried

data2['columnF'] = data1['columnF'] #doesn't work

also tried

data1['columnF'] = '' #adding a columnF to data1 merg_left = pd.merge(left=data1,right=data2, how='left', left_on='columnF', right_on='columnF') #gave me a weird output file

You need to add more detail. Do they have the same index? if so then data2['columnF'] = data1['columnF'] would work. Are the same shape? Do they have some common index? pd.concat is probably what you want to use but until we know what the indices and shape are we can't tell you exactly how to use it. — JoeCondron
– JoeCondron, Commented Nov 4, 2015 at 21:28

Butiri Dan · Accepted Answer · 2019-11-29 08:01:57Z

18

import pandas as pd f_column = data2["columnF"] data1 = pd.concat([data1,f_column], axis = 1) data1

 columnA columnB columnC columnF 0 a b c f 1 a b c f 2 a b c f

edited Nov 29, 2019 at 8:01

Butiri Dan

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answered Nov 29, 2019 at 6:56

Nisarg Nikhil

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Comments

Leb · Accepted Answer · 2015-11-04 21:30:31Z

15

import pandas as pd import io data = """ ColumnA columnB columnC columnD A B C D A B C D A B C D """ data1 = """ ColumnE columnF columnG E F G E F G E F G """ df = pd.read_csv(io.StringIO(data), delimiter='\s+') df1 = pd.read_csv(io.StringIO(data1), delimiter='\s+') df['columnF'] = pd.Series(df1['columnF']) print(df)

Will give you:

 ColumnA columnB columnC columnD columnF 0 A B C D F 1 A B C D F 2 A B C D F

answered Nov 4, 2015 at 21:30

Leb

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4 Comments

Jessica Over a year ago

thank you! i think i understand your code but the data and data1 are 2 files that i have read in using pd.read_csv and pd.read_excel, instead of the simple tables i put up there (wanted to make everything look clean here), and when i assign io.StringIO(data) and io.StringIO(data1) the error message gave "initial_value must be str or None, not DataFrame" , do you know how i should fix this? thanks

Leb Over a year ago

The io.StringIO() are just a way to create your sample data. You should use read_csv and read_excel as you have. The main part is df['columnF'] = pd.Series(df1['columnF'])

Jessica Over a year ago

thanks that worked. if i want to insert that 'columnF' from df1 to the column after 'columnA' in df, would i do something like df['columnA'+1] = df['columnF'] ?

Leb Over a year ago

That won't work. You'll need insert for that. df.insert(1,'columnF',df1['columnF'])

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