python – How to add a new column to a CSV file?

python – How to add a new column to a CSV file?

This should give you an idea of what to do:

>>> v = open(C:/test/test.csv)
>>> r = csv.reader(v)
>>> row0 = r.next()
>>> row0.append(berry)
>>> print row0
[Name, Code, berry]
>>> for item in r:
...     item.append(item[0])
...     print item
...     
[blackberry, 1, blackberry]
[wineberry, 2, wineberry]
[rasberry, 1, rasberry]
[blueberry, 1, blueberry]
[mulberry, 2, mulberry]
>>> 

Edit, note in py3k you must use next(r)

Thanks for accepting the answer. Here you have a bonus (your working script):

import csv

with open(C:/test/test.csv,r) as csvinput:
    with open(C:/test/output.csv, w) as csvoutput:
        writer = csv.writer(csvoutput, lineterminator=n)
        reader = csv.reader(csvinput)

        all = []
        row = next(reader)
        row.append(Berry)
        all.append(row)

        for row in reader:
            row.append(row[0])
            all.append(row)

        writer.writerows(all)

Please note

1. the lineterminator parameter in csv.writer. By default it is
   set to rn and this is why you have double spacing.
2. the use of a list to append all the lines and to write them in
   one shot with writerows. If your file is very, very big this
   probably is not a good idea (RAM) but for normal files I think it is
   faster because there is less I/O.

3. As indicated in the comments to this post, note that instead of
   nesting the two with statements, you can do it in the same line:

   with open(C:/test/test.csv,r) as csvinput, open(C:/test/output.csv, w) as csvoutput:

Im surprised no one suggested Pandas. Although using a set of dependencies like Pandas might seem more heavy-handed than is necessary for such an easy task, it produces a very short script and Pandas is a great library for doing all sorts of CSV (and really all data types) data manipulation. Cant argue with 4 lines of code:

import pandas as pd
csv_input = pd.read_csv(input.csv)
csv_input[Berries] = csv_input[Name]
csv_input.to_csv(output.csv, index=False)

Check out Pandas Website for more information!

Contents of output.csv:

Name,Code,Berries
blackberry,1,blackberry
wineberry,2,wineberry
rasberry,1,rasberry
blueberry,1,blueberry
mulberry,2,mulberry

python – How to add a new column to a CSV file?

import csv
with open(input.csv,r) as csvinput:
    with open(output.csv, w) as csvoutput:
        writer = csv.writer(csvoutput)

        for row in csv.reader(csvinput):
            if row[0] == Name:
                writer.writerow(row+[Berry])
            else:
                writer.writerow(row+[row[0]])

Maybe something like that is what you intended?

Also, csv stands for comma separated values. So, you kind of need commas to separate your values like this I think:

Name,Code
blackberry,1
wineberry,2
rasberry,1
blueberry,1
mulberry,2