ValueError: invalid literal for int() with base 10 reading CSV

Question

Below is my code but I'm getting ValueError. My input is from CSV file containing integers, but unable to import them:

import csv

excel_1 = open(r"C:\Users\JP Dayao\Desktop\Python files\test_file.csv")
raw_1 = csv.reader(excel_1)
t_ijklm = []

for i in raw_1:
    for j in i:
        t_ijklm.append(int(j))
excel_1.close()

Output (with error):

ValueError                                Traceback (most recent call last)
Input In [5], in <cell line: 17>()
     17 for i in raw_1:
     18     for j in i:
---> 19         t_ijklm.append(int(j))
     20 excel_1.close()
     22 #import constraints data

ValueError: invalid literal for int() with base 10:

Contents of CSV file:

21;19;21;19;24;23;35;35;36;35;36;35;35;23;22;30;23;36;23;26;25;25;40;25;40;25;22;21;21;25;20;25;22;22;18;19;25;18;25;17;23;20;24;24;22;24;21;22;23;21;27;22;36;23;25;29;29;23;28;33;29;31;19;26;32;20;35

Answer 1

By default, the csv module expects the file to be a proper .csv file. CSV stands for Comma Separated Values, so the values in the file should be separated by commas, like

21,19,21,19,24,23,35,35,36,35,36,35,35,23,22,30,23,36,23,26,25,25,40,25,40,25,22,21,21,25,20,25,22,22,18,19,25,18,25,17,23,20,24,24,22,24,21,22,23,21,27,22,36,23,25,29,29,23,28,33,29,31,19,26,32,20,3

The error suggests that your data is in fact separated with semicolons instead, like:

21;19;21;19;24;23;35;35;36;35;36;35;35;23;22;30;23;36;23;26;25;25;40;25;40;25;22;21;21;25;20;25;22;22;18;19;25;18;25;17;23;20;24;24;22;24;21;22;23;21;27;22;36;23;25;29;29;23;28;33;29;31;19;26;32;20;3

Since there are no commas, the entire line is treated as a single column.

you can tell the CSV module to use ; as the sepreator (delimiter) not comma. Do this by passing delimiter=";" to the csv.reader method, like so:

import csv

excel_1 = open(r"test_file.csv")
raw_1 = csv.reader(excel_1, delimiter=";")
t_ijklm = []

for i in raw_1:
    for j in i:
        t_ijklm.append(int(j))
excel_1.close()

As an aside, it is better to open the file using a with block:

import csv

with open(r"test_file.csv") as excel_1:
    raw_1 = csv.reader(excel_1, delimiter=";")
    t_ijklm = []

    for i in raw_1:
        for j in i:
            t_ijklm.append(int(j))

Answer 2

You need to add a delimeter in the csv.reader function. for example:

with open(r"C:\Users\JP Dayao\Desktop\Python files\test_file.csv") as csvfile:
  file_reader = csv.reader(csvfile, delimiter=';')
  for row in file_reader:
    --your code--

Hope it helps!