CODEWITHSUNDEEP
pythoncsvmatrixtranspose
Heinz
Heinz

Reputation: 2467

Python CSV transpose data in one column to rows

I have a CSV file containing data only in the first column,

enter image description here

I want to use python to transpose every 4 rows to another empty CSV file, for example, row 1 to row 4 transposed to the first row; then row 5 to row 8 transposed to the second row,...etc, and finally we can get a 5 * 4 matrix in the CSV file.

enter image description here

How to write a script to do this？ Please give me any hint and suggestion, thank you.

I am using python 2.7.4 under Windows 8.1 x64.

update#1

I use the following code provided by thefortheye,

import sys, os
os.chdir('C:\Users\Heinz\Desktop')
print os.getcwd()

from itertools import islice
with open("test_csv.csv") as in_f, open("Output.csv", "w") as out_file:
    for line in ([i.rstrip()] + map(str.rstrip, islice(in_f, 3)) for i in in_f):
        out_file.write("\t".join(line) + "\n")

the input CSV file is,

enter image description here

and the result is,

enter image description here

This is not what I want.

Upvotes: 2

Views: 2177

Answers (2)

thefourtheye
thefourtheye

Reputation: 239443

You can use List comprehension like this

data = range(20)
print data
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
print[data[i:i + 4] for i in xrange(0, len(data), 4)]
# [[0, 1, 2, 3], [4, 5, 6, 7], [8, 9, 10, 11], [12, 13, 14, 15], [16, 17, 18,19]]

Instead of 4, you might want to use 56.

Since you are planing to read from the file, you might want to do something like this

from itertools import islice
with open("Input.txt") as in_file:
    print [[int(line)] + map(int, islice(in_file, 3)) for line in in_file]

Edit As per the updated question,

from itertools import islice
with open("Input.txt") as in_f, open("Output.txt", "w") as out_file:
    for line in ([i.rstrip()] + map(str.rstrip, islice(in_f, 3)) for i in in_f):
        out_file.write("\t".join(line) + "\n")

Edit: Since you are looking for comma separated values, you can join the lines with ,, like this

        out_file.write(",".join(line) + "\n")

Upvotes: 1

Kei Minagawa
Kei Minagawa

Reputation: 4501

You can use List comprehension and double-loop like this.

>>> M = 3
>>> N = 5
>>> a = range(M * N)
>>> o = [[a[i * N + j] for j in xrange(N)] for i in xrange(M)]
>>> print o
[[ 0,  1,  2,  3,  4],
 [ 5,  6,  7,  8,  9],
 [10, 11, 12, 13, 14]]

Upvotes: 0

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