Python saving data from lists into columns in a CSV

Question

My list is generated dynamically each time, but for this example the list can be a basic range of 0 - 24. The list is split by my function and written to a CSV file. Here is a bit of the code:

numSeq = range(25)

def split_list(alist, rows):
    length = len(alist)
    return [alist [i*length // rows: (i+1)*length // rows] for i in range(rows)]

with open(csvfile, "w") as output:
    writer = csv.writer(output, lineterminator='\n')
    writer.writerows(split_list(numSeq, 5))

This pretty much works fine. The problem is, I want to split it into columns not rows. Specifically, it is writing to the CSV like this:

00,01,02,03,04
05,06,07,08,09
10,11,12,13,14
15,16,17,18,19
20,21,22,23,24

However, I need it to split & write like this:

00,05,10,15,20
01,06,11,16,21
02,07,12,17,22
03,08,13,18,23
04,09,14,19,24

Any idea on how I could go about doing this? Thanks in advance!

Sorry for poor formatting, I'm on mobile!

Check out the solution at: stackoverflow.com/questions/10507104/… — Dominic Larkin
– Dominic Larkin, Commented Dec 9, 2015 at 5:40

Ozgur Vatansever · Accepted Answer · 2015-12-09 05:36:53Z

4

You can transpose the resulting list using zip() function:

writer.writerows(zip(*split_list(numSeq, 5)))

Example:

>>> lst = [[1, 2, 3], [4, 5, 6]]
>>> zip(*lst)
[(1, 4), (2, 5), (3, 6)]

answered Dec 9, 2015 at 5:36

Ozgur Vatansever

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1 Comment

dimensive Over a year ago

This worked great! I did not know zip() worked that simply. Thanks for the quick answer.

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