Writing Python lists to columns in csv

Question

I have 5 lists, all of the same length, and I'd like to write them to 5 columns in a CSV. So far, I can only write one to a column with this code:

with open('test.csv', 'wb') as f:
    writer = csv.writer(f)
    for val in test_list:
        writer.writerow([val])

If I add another for loop, it just writes that list to the same column. Anyone know a good way to get five separate columns?

Answer 1

change them to rows

rows = zip(list1,list2,list3,list4,list5)

then just

import csv

with open(newfilePath, "w") as f:
    writer = csv.writer(f)
    for row in rows:
        writer.writerow(row)

Answer 2

The following code writes python lists into columns in csv

import csv
from itertools import zip_longest
list1 = ['a', 'b', 'c', 'd', 'e']
list2 = ['f', 'g', 'i', 'j']
d = [list1, list2]
export_data = zip_longest(*d, fillvalue = '')
with open('numbers.csv', 'w', encoding="ISO-8859-1", newline='') as myfile:
      wr = csv.writer(myfile)
      wr.writerow(("List1", "List2"))
      wr.writerows(export_data)
myfile.close()

The output looks like this

Answer 3

You can use izip to combine your lists, and then iterate them

for val in itertools.izip(l1,l2,l3,l4,l5):
    writer.writerow(val)

Answer 4

If you are happy to use a 3rd party library, you can do this with Pandas. The benefits include seamless access to specialized methods and row / column labeling:

import pandas as pd

list1 = [1, 2, 3]
list2 = [4, 5, 6]
list3 = [7, 8, 9]

df = pd.DataFrame(list(zip(*[list1, list2, list3]))).add_prefix('Col')

df.to_csv('file.csv', index=False)

print(df)

   Col0  Col1  Col2
0     1     4     7
1     2     5     8
2     3     6     9

Answer 5

I didn't want to import anything other than csv, and all my lists have the same number of items. The top answer here seems to make the lists into one row each, instead of one column each. Thus I took the answers here and came up with this:

import csv
list1 = ['a', 'b', 'c', 'd', 'e']
list2 = ['f', 'g', 'i', 'j','k']
with open('C:/test/numbers.csv', 'wb+') as myfile:
    wr = csv.writer(myfile)
    wr.writerow(("list1", "list2"))
    rcount = 0
    for row in list1:
        wr.writerow((list1[rcount], list2[rcount]))
        rcount = rcount + 1
    myfile.close()

Answer 6

I just wanted to add to this one- because quite frankly, I banged my head against it for a while - and while very new to python - perhaps it will help someone else out.

 writer.writerow(("ColName1", "ColName2", "ColName"))
                 for i in range(len(first_col_list)):
                     writer.writerow((first_col_list[i], second_col_list[i], third_col_list[i]))

Answer 7

import csv
dic = {firstcol,secondcol} #dictionary
csv = open('result.csv', "w") 
for key in dic.keys():
    row ="\n"+ str(key) + "," + str(dic[key]) 
    csv.write(row)