How to convert string values to integer values while reading a CSV file?

Question

When opening a CSV file, the column of integers is being converted to a string value ('1', '23', etc.). What's the best way to loop through to convert these back to integers?

import csv

with open('C:/Python27/testweight.csv', 'rb') as f:
    reader = csv.reader(f)
    rows = [row for row in reader if row[1] > 's']

for row in rows:
    print row

CSV file below:

Account Value
ABC      6
DEF      3
GHI      4
JKL      7

Solution 1

I think this does what you want:

import csv

with open('C:/Python27/testweight.csv', 'r', newline='') as f:
    reader = csv.reader(f, delimiter='\t')
    header = next(reader)
    rows = [header] + [[row[0], int(row[1])] for row in reader if row]

for row in rows:
    print(row)

Output:

['Account', 'Value']
['ABC', 6]
['DEF', 3]
['GHI', 4]
['JKL', 7]

Solution 2

If the CSV has headers, I would suggest using csv.DictReader. With this you can do:

 with open('C:/Python27/testweight.csv', 'rb') as f:
    reader = csv.DictReader(f)
    for row in reader:
        integer = int(row['Name of Column'])

Solution 3

You could just iterate over all of the rows as follows:

import csv

with open('testweight.csv', newline='') as f:
    rows = list(csv.reader(f))      # Read all rows into a list

for row in rows[1:]:    # Skip the header row and convert first values to integers
    row[1] = int(row[1])

print(rows)

This would display:

[['Account', 'Value'], ['ABC', 6], ['DEF', 3], ['GHI', 4], ['JKL', 7]]

Note: your code is checking for > 's'. This would result in you not getting any rows as numbers would be seen as less than s. If you still use Python 2.x, change the newline='' to 'rb'.

Comments

[JSmooth]

Thanks, but I am getting a KeyError: 1

[Jasper van den Berg]

This means there is a fault in the csv, would you mind posting a little part of the csv with the header?

[JSmooth]

I put it in original question

[Jasper van den Berg]

The column you want to fetch needs to by typed as a string, so: integer = int(row['1']). Do not forget the quotes!!!

[JSmooth]

Thanks, but that is giving me "IndexError: list index is out of range"

[JSmooth]

Do I have to specify the range, and if so, where?

[martineau]

Sounds like some of the rows in the real .CSV file don't contain two values. If that's the case, you could skip them by changing the end of the list comprehension to ...for row in reader if len(row) > 1].