Writing a list to a csv file in Python

Question

I am in Python and have a list of numbers that I want to write to a csv file. Say, my list is: [1 2 3 4 5 6 7 8 9], and within the csv file to which I am exporting this data, I want to begin a new line every three numbers. Meaning, when I open my output file in Excel, I want it to look like this.

So, I essentially want to take a 9 element list and write it into a 3x3 matrix. I'm sure I must end up using the writerows command, but have not been able to find documentation of a problem similar enough to mine, so I am not sure exactly what to do with it.

Any help would be greatly appreciated, and I'm sorry if this question has already been asked at some point.

Answer 1

slice your list into a 2D list using a comprehension, and pass that to csv.writerows .

Self-contained example:

import csv

lst = list(range(1,10))

with open("out.csv","w",newline="") as f:
    cw = csv.writer(f)
    cw.writerows(lst[i:i+3] for i in range(0,len(lst),3))

creates a csv file like this:

1,2,3
4,5,6
7,8,9

Answer 2

You can use reshape :

import numpy
my_array=numpy.reshape(my_list, (3,3))

BTW, it should be [1, 2, 3, 4, 5, 6, 7, 8, 9] , not [1 2 3 4 5 6 7 8 9]