Sorting a csv file (Python)

Question

I have this piece of code written to sort a csv file in Python.

import csv
from operator import itemgetter
reader = csv.reader(open("highscores.txt"), delimiter=",")
sortedList = sorted(reader, key=itemgetter(1), reverse=True)
print(sortedList)

I am trying the sort the file by the second item in the array, for example if in my file I had:

Callum,22
Kim,43

It would sort it to:

Kim,43
Callum,22

However when I run my program I get the error message:

sortedList = sorted(reader, key=itemgetter(1), reverse=True)
IndexError: list index out of range

Edit:

I have solved this issue, the problem wasn't the sort function itself but it was a problem with the file that only worked in python 2.7 for some reason.

Possible duplicate of Sorting by Specific Column data using .csv in python — ilim
– ilim, Commented Feb 6, 2017 at 14:42
It works fine on python3.5. Is it possible that the input file has an empty line or maybe missing scores on a line? Try an input file with just the two lines of input as you listed above. Does that work? — greedy52
– greedy52, Commented Feb 6, 2017 at 15:05

Ketan · Accepted Answer · 2017-02-06 15:34:59Z

1

You can use lambda which will allow you to do type transform etc. Similar to your example above, following lines will do what you want (I have kept sort etc default):

r = csv.reader(open("test.txt"))
sorted(r, key=lambda x: int(x[1]))

You can read more details at https://wiki.python.org/moin/HowTo/Sorting

These are full details showing version and platform:

Python 2.7.10 (default, Jul 30 2016, 18:31:42) 
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import csv
>>> r = csv.reader(open("test.txt"))
>>> sorted(r, key=lambda x: int(x[1]))
[['Can', ' 2'], ['Try', ' 5'], ['Science', ' 12'], ['Math', ' 22'], ['Life', ' 35']]

where test.txt is as below:

Science,12
Math,22
Life,35
Can,2
Try,5

edited Feb 6, 2017 at 15:34

answered Feb 6, 2017 at 14:59

Ketan

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3 Comments

Ketan Over a year ago

See added details above. Can you just write content on screen as: > for line in reader: print line

Callum Over a year ago

The problem is due to python 3 I think, just tried on python 2.7.12 and both methods are now working.

Ketan Over a year ago

That is good to know but not useful. CSV reader and sorted both should behave the same unless default arguments have changed. Did you try to write out each line read by reader on console, as suggested above? It will be good to confirm what change is failing for you.

zipa · Accepted Answer · 2017-02-06 16:14:48Z

0

My assumption is that you are missing some data. Here is my workaround for that case:

import csv

with open("highscores.txt") as data:
    data = csv.reader(data)
    data = [item for item in data]
    for i, item in enumerate(data):
        try:
            item = int(item[1])
        except:
            data[i].append('0')
    items = sorted(data, key=lambda x: int(x[1]), reverse=True)
    print(items)

answered Feb 6, 2017 at 16:14

zipa

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