Question

sort csv by column

I want to sort a CSV table by date. Started out being a simple task:

import sys
import csv

reader = csv.reader(open("files.csv"), delimiter=";")

for id, path, title, date, author, platform, type, port in reader:
    print date

I used Python's CSV module to read in a file with that structure:

id;file;description;date;author;platform;type;port
  • The date is ISO-8601, therefore I can sort it quite easily without parsing: 2003-04-22 e. g.
  • I want to sort the by date, newest entries first
  • How do I get this reader into a sortable data-structure? I think with some effort I could make a datelist: datelist += date, split and sort. However I have to re-identify the complete entry in the CSV table. It's not just sorting a list of things.
  • csv doesn't seem to have a built in sorting function

The optimal solution would be to have a CSV client that handles the file like a database. I didn't find anything like that.

I hope somebody knows some nice sorting magic here ;)

 45  151357  45
1 Jan 1970

Solution

 85

Since 'date' in column has index 3,

import operator
sortedlist = sorted(reader, key=operator.itemgetter(3), reverse=True)

or use lambda

sortedlist = sorted(reader, key=lambda row: row[3], reverse=True)
2010-01-20

Solution

 23

To sort by MULTIPLE COLUMN (Sort by column_1, and then sort by column_2)

with open('unsorted.csv',newline='') as csvfile:
    spamreader = csv.DictReader(csvfile, delimiter=";")
    sortedlist = sorted(spamreader, key=lambda row:(row['column_1'],row['column_2']), reverse=False)


with open('sorted.csv', 'w') as f:
    fieldnames = ['column_1', 'column_2', column_3]
    writer = csv.DictWriter(f, fieldnames=fieldnames)
    writer.writeheader()
    for row in sortedlist:
        writer.writerow(row)
2017-05-16