python 3 IndexError: list index out of range -

my problem average value on won't show returns error

traceback (most recent call last): (file location), line 29, in <module>     average_score = [[x[8],x[0]] x in a_list] (file location), line 29, in <listcomp>     average_score = [[x[8],x[0]] x in a_list]  indexerror: list index out of range 

the code

   import csv class_a = open('class_a.txt') csv_a = csv.reader(class_a) a_list = [] row in csv_a:     row[3] = int(row[3])     row[4] = int(row[4])     row[5] = int(row[5])     minimum = min(row[3:5])     row.append(minimum)     maximum = max(row[3:5])     row.append(maximum)     average = sum(row[3:5])//3     row.append(average)     a_list.append(row[0:8]) print(row[8]) 

this works when test out values 0 7 ,even if change location of avarage sum still error

when call a_list.append(row[0:8]) you're appending array using indexes 0, 1, 2, 3, 4, 5, 6, , 7 row. means when later iterate a_list, x variable has indexes 7, , you're trying access 8.

quick example:

>>> row = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] >>> x = row[:8] >>> x[8] traceback (most recent call last):   file "<stdin>", line 1, in <module> indexerror: list index out of range >>> x[7] 7 >>>