Sum a csv column in python

csv, python, sum

Solution

The `csv` module loops over your rows one by one, there is no need to then loop over the column. Just sum `int(row[1])`:

with open("file.csv") as fin:
    headerline = next(fin)
    total = 0
    for row in csv.reader(fin):
        total += int(row[1])
    print(total)

You can use a shortcut with a generator expression and the `sum()` built-in function:

with open("file.csv") as fin:
    next(fin)
    total = sum(int(r[1]) for r in csv.reader(fin))

Note that in Python, strings are sequences too, so when you do `for col in row[1]:` you are looping over the individual characters of `row[1]`; so for your first row that'd be `1` and `2`:

>>> for c in '123':
...     print(repr(c))
...
'1'
'2'
'3'

Problem

I'm trying to make a sum of a column in a csv file. The file looks like: ``` Date Value 2012-11-20 12 2012-11-21 10 2012-11-22 3 ``` This can be in the range of hundreds of rows. I need to get the total of Value (in this case it would be 25) printed on to a terminal. I so far have some code but it's resulting in a much smaller figure than it should sum. When troubleshooting it, I did a print of the sum and realized that instead of summing 12 + 10 + 3, it actually breaks the numbers in each column and sums as 1 + 2 + 1 + 0 + 3, which obviously equals to a much smaller total. Here's my code, if someone could make a recommendation would be great! ``` with open("file.csv")) as fin: headerline = fin.next() total = 0 for row in csv.reader(fin): print col # for troubleshooting for col in row[1]: total += int(col) print total ```

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