Python sort CSV File

Question

Hey I have a CSV file with many rows but one of the row constantly repeats. Is it possible to only keep the first name for that row and keep all other data. I tried with pandas but pandas asks for a function such as aggregate sum. My data in the CSV file is like.

H1 h2 h3 h4
A 1 2 3 4
A 2 3 4 5
A 3 4 5 6
B 1 2 3 4
B 2 3 4 5
B 3 4 5 6
C 1 2 3 4
C 2 3 4 5
C 3 4 5 6

Each one of these has a header. Which are shown by h1-h4. My data is not like this, it contains real text values.

I want to rearrange the data so it looks like this.

A 
   1 2 3 4
   2 3 4 5
   3 4 5 6
B
   1 2 3 4
   2 3 4 5
   3 4 5 6

C
   1 2 3 4
   2 3 4 5
   3 4 5 6

Or

 A 1 2 3 4
   2 3 4 5
   3 4 5 6

B  1 2 3 4
   2 3 4 5
   3 4 5 6

C  1 2 3 4
   2 3 4 5
   3 4 5 6

So basically I want it to group by the first header name which is h1. Any help would be appreciated thanks.

Answer 1

The following should work, it assumes your source data is space delimited (as you have shown), if it uses commas or tabs, you will need to change the delimiter I have used.

import csv

with open("input.csv", "r") as f_input, open("output.csv", "wb") as f_output:
    csv_input = csv.reader(f_input, delimiter=" ")
    csv_output = csv.writer(f_output)
    headers = next(csv_input)

    cur_row = ""
    for cols in csv_input:
        if cur_row != cols[0]:
            cur_row = cols[0]
            csv_output.writerow([cur_row])
        csv_output.writerow(cols[1:])

Giving you an output CSV file as follows:

A
1,2,3,4
2,3,4,5
3,4,5,6
B
1,2,3,4
2,3,4,5
3,4,5,6
C
1,2,3,4
2,3,4,5
3,4,5,6

Tested using Python 2.7

To add the headers for each group, change the first writerow line as follows:

csv_output.writerows([[cur_row], headers])

Giving the following output:

A
H1,h2,h3,h4
1,2,3,4
2,3,4,5
3,4,5,6
B
H1,h2,h3,h4
1,2,3,4
2,3,4,5
3,4,5,6
C
H1,h2,h3,h4
1,2,3,4
2,3,4,5
3,4,5,6