Traceback error when handling text files

Question

I have created this code, which performs a quiz and then writes the result to a text file based on a user input (class). All the file handling code seems sound to me, but when I run the program, I experience a "Traceback (most recent call last): Traceback (most recent call last):" error, and then the program crashes out.

I just had the same problem with a different bit of code and got an answer, but I have not made the error I made again (trying to write multiple variables to a file at once), so that answer isn't applicable this time.

import random 

forename="" 
surname=""
classno=0
numberone=0 
numbertwo=0
correct=False
score=0
ops = ["+", "x", "-"] 



while forename == "" or forename.isnumeric():
    forename=input("What is your first name? ")
    if forename == "": 
        print("You have to enter your first name.")
    if forename.isnumeric() == True:
        print("Your name must contain letters.")

while surname == "" or surname.isnumeric():
    surname=input("What is your surname? ")
    if surname == "":
        print("You have to enter your name.")
    if surname.isnumeric() == True:
        print("Your name must contain letters.")

while classno not in [1,2,3]: 
    while True:
        try:
            classno=int(input("What class are you in? "))
            break
        except ValueError:
            print("That wasn't right. Please try again.")



for x in range(10): 
    operation=random.choice(ops) 

if operation == "-": 
    numberone=random.randint(0,10) 
    numbertwo=random.randint(0,numberone)

elif operation == "x":
    numberone=random.randint(0,12)
    numbertwo=random.randint(0,12) 

else:
    numberone=random.randint(0,100)
    numbertwo=random.randint(0,(100-numberone))

while True:
        try:
            answer=int(input("What is " + str(numberone) + str(operation) + str(numbertwo) + "? "))
            break 
        except ValueError: 
            print("Incorrect input. Please try again.")


if operation=="+":
    if answer==numberone+numbertwo:
        correct=True

elif operation=="-":
    if answer==numberone-numbertwo:
        correct=True

else:
    if answer==numberone*numbertwo:
        correct=True

if correct==True:
    print("Correct!")
    score=score+1

else:
    print("Wrong!")

correct = False



info = str(forename) + "," + str(surname) + "," + str(score) + "\n"    



if classno == 1:
    file=open("class1.txt", "a")

elif classno == 2:
    file=open("class2.txt", "a")

else:
    file=open("class3.txt", "a")


maxnames = sum(1 for line in file)
name = [[] for i in range(maxnames)]   #creates empty list


for count in range(maxnames):
    line = file.readline()   #defines one line
    line=line.strip("\n")   #defines where lines end
    data = line.split(",")  #defines each data particle

    name[count].append(data[0])   #puts name in
    name[count].append(data[1])   #puts scores in
    name[count].append(data[2])
    name[count].append(data[3])


if forename == name[c][0] and surname == name[c][1]:
    name[c][4]=name[c][3]
    name[c][3]=name[c][2]
    name[c][2]=score
else:
    file.write(info)

file.close()


print("You scored",score,"out of 10.")

Here's what I'm seeing:

Answer 1

The problem begins with the fact that you're opening a file for writing (by using the 'a' mode) and then trying to read from it. If you change that to 'r+' the problem may solve itself. Without an actual traceback there's no way to know for sure.