python csv add column values based on another column

Question

I have a two column csv file

    row    vote
     1      0
     1      0
     1      1
     2      0
     2      0
     3      1
     3      0

I'm trying to write a python script so that each vote is counted depending on the row number, thus outputting

   row    vote
    1      1
    2      0
    3      1

what I've tried so far with a text file:

from collections import defaultdict

d = defaultdict(int)

with open("data.txt") as f:
    for line in f:
        tokens = [t.strip() for t in line.split(",")]
        try:
            row = int(tokens[1])
            vote = int(tokens[1])
        except ValueError:
            continue
        d[row] += vote
print d

and I'm getting IndexError: list index out of range errors

could you fix your indentation in code you posted ?

ThePavolC
– ThePavolC

2015-05-03 18:05:46 +00:00
Commented May 3, 2015 at 18:05 — ThePavolC
– ThePavolC, Commented May 3, 2015 at 18:05
Shouldn't it be row = int(tokens[0])?

Adalee
– Adalee

2015-05-03 18:09:44 +00:00
Commented May 3, 2015 at 18:09 — Adalee
– Adalee, Commented May 3, 2015 at 18:09

ThePavolC · Accepted Answer · 2015-05-03 18:20:09Z

1

As @Adalee mentioned, you probably should have row = int(tokens[0]).

Here is one way to do this:

result = {}

with open("test.csv") as f:
    for line in f:
        tokens = line.split(",")

        row = None
        vote = None

        try:
            row = int(tokens[0])
            vote = int(tokens[1])
        except Exception as e:
            pass

        if row is not None:
            if result.has_key(row):
                result[row] += vote
            else:
                result[row] = vote

print result

And output could be:

{1: 1, 2: 3, 3: 9}

test.csv file:

row,vote
1,0
1,0
1,1
2,2
2,1
3,4
3,2
3,3

answered May 3, 2015 at 18:20

ThePavolC

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