Writing a .csv file from a list in Python

full = {}
arr = []

with open('numbers.txt', 'r') as nums:
    while True:
        read = nums.readline()
        if len(read) > 0:
            if len(read) == 6:
                read = read[:5]
                arr.append(read)
            elif len(read) < 6:
                read = read[0]
                full[read] = arr
                arr = []
        else:
            break

with open('numbers.csv', 'w') as csv:
    for i in full:
        for j in full[i]:
            line = str(j) + ',' + str(i) + '\n'
            csv.write(line)

This file takes a text file (I copied what you posted above and saved to a text file) and outputs it in a .csv file the way you described.

Sorry for lack of comments, I did it quickly. If you want to modify and don't understand anything just ask and I'll explain.

Also, the way it is now, the program will only work for single digit group numbers. The following change will fix this for numbers up to 4 digits (obviously 5 digits will break it because it won't be able to differentiate between set numbers and their containing elements:

Change the line

read = read[0]

to

read = read[0:len(read)-2]

and it works. Except that it orders them alphabetically rather than numerically, so it goes 11, 10, 1, 2, 3, 4, 5, 6, 7, 8, 9.

This page provides a thorough overview: http://docs.python.org/library/csv.html

And here on this page it gives you a simple example: http://www.answermysearches.com/list-to-csv-in-10-seconds-python-csv-module-quick-reference/120/

import csv

f = open("input.txt", "r")
o = open("output.csv", "wb")
csvo = csv.writer(o)

inputText = f.read().split(";")
f.close()

for block in inputText:
    row = data.split("\n")
    idNo = row[-1]
    numbers = ""
    for line in row[:-1]:
        numbers += line +"\n"
    numbers.strip("\n")
    csvo.writerow([idNo, numbers])


o.flush()
o.close()

What this script does, is using the semi-colon as a delimiter, it will split the data out into sets. From this, it then splits it by row, to give a list of the 5-digit numbers, and the group number at the end. So it takes the last number from the list and places it into the first column, and the rest, it will place into the second column, delimited by a newline.

Hope this helps