write a Python 3 list to .csv

Question

I have a list that i need to write to a .csv Yes, i have done a LOT of looking around (of course i found this link which is close to the target, but misses my case) You see writerows is having all sorts of trouble with the delimiters/formatting in the .csv (the a gets separated from the 1 from the 7 etc etc)

My list looks like this:

buffer = [['a17', 'b17', 'c17', '8', 'e17', 'f17\n'], ['a24', 'b24', 'c24', '6', 'e24', 'f24\n'], ['a27', 'b27', 'c27', '9', 'e27', 'f27\n'], ['a18', 'b18', 'c18', '9', 'e18', 'f18\n'], ['a5', 'b5', 'c5', '5', 'e5', 'f5\n'], ['a20', 'b20', 'c20', '2', 'e20', 'f20\n'], ['a10', 'b10', 'c10', '1', 'e10', 'f10\n'], ['a3', 'b3', 'c3', '3', 'e3', 'f3\n'], ['a11', 'b11', 'c11', '2', 'e11', 'f11\n']]

I can see its like a list of lists so i tried for eachRow in buffer: then following on with a eachRow.split(',') but no good there either. I just need to write to a .csv it should be easy right... what am i missing?

score 2 · Answer 1 · answered Mar 15 '16 at 06:06

2

import csv
with open('output.csv','w') as f:
    writer = csv.writer(f)
    writer.writerows(buffer)

Note that the last entry in each of your lists has a newline, so the csvwriter is correctly quoting the string so you end up with "f17\n" (in the first list as an example) which will look strangely formatted if you are not expecting a new line.

answered Mar 15 '16 at 06:06

GarMan

1,034
7
10

i can't believe i was so close. you are great! That's a cool start and as you suggested the newlines are adding blank rows. So what do you suggest is the cleanest way to get rid of the `\n` newlines? (They just seem to be there when i read the source .csv file) – sixD Mar 15 '16 at 06:16
I tried `lineAsList = [i.strip() for i in a]` which removes the `\n`s from `buffer` but the .csv STILL has every second row blank... any thoughts? – sixD Mar 15 '16 at 07:10
I addressed your question in my answer. – Igor Mar 15 '16 at 22:22

score 2 · Accepted Answer · edited Jan 03 '18 at 09:56

You can remove the \n string from your buffer like so. Also you have to add newline='' to the with statement in Python 3. See this answer for more detail.

import csv


buffer = [['a17', 'b17', 'c17', '8', 'e17', 'f17\n'],
          ['a24', 'b24', 'c24', '6', 'e24', 'f24\n'],
          ['a27', 'b27', 'c27', '9', 'e27', 'f27\n'],
          ['a18', 'b18', 'c18', '9', 'e18', 'f18\n'],
          ['a5', 'b5', 'c5', '5', 'e5', 'f5\n'],
          ['a20', 'b20', 'c20', '2', 'e20', 'f20\n'],
          ['a10', 'b10', 'c10', '1', 'e10', 'f10\n'],
          ['a3', 'b3', 'c3', '3', 'e3', 'f3\n'],
          ['a11', 'b11', 'c11', '2', 'e11', 'f11\n']]

for row_index, list in enumerate(buffer):
    for column_index, string in enumerate(list):
        buffer[row_index][column_index] = buffer[row_index][column_index].replace('\n', '')

with open('output.csv', 'w', newline='') as f:
    writer = csv.writer(f)
    writer.writerows(buffer)

write a Python 3 list to .csv

2 Answers2