需要解释为什么我的代码会产生ValueError

Question

I am very new to python and have been struggling with this issue for quite some time now. I don't understand that why is my code producing this error message and abruptly stops in between:

Traceback (most recent call last):
File "C:/...some path../Random_marks.py", line 70, in <module>
total_marks = int(total)
ValueError: invalid literal for int() with base 10: 'A\n'

From what I understand is that it is never going in the if statement in line number 66 (marked with a comment below) of my code. But I don't understand why and how to fix it? Variable total is of string type only, so isalpha() should return True . But when I print it, it says False for some reason.

Here is the enitre code, but problems are only in the while loop at the bottom I guess.

from random import *

infile = open("Compb12-81test1.txt", "r")
outfile = open("Compb12-81test1_marks.txt", "w")

def alldone(done):
    for i in done:
        if i == 0:
            return False
    return True

def assign2m(marks,done,total):
    extra = randint(0,5)
    done[extra] = 1
    while not alldone(done[0:6]):
        mark = randint(0,2)
        select = randint(0,5)
        if total - mark >= 0 and done[select] == 0 and select != extra:
            total -= mark
            marks[select] = mark
            done[select] = 1
    return total

def assign5m(marks,done,total):
    extra1 = randint(6,7)
    extra2 = randint(8,9)
    done[extra1] = 1
    done[extra2] = 1
    while not alldone(done[6:10]):
        mark = randint(0,5)
        select = randint(6,9)
        if total - mark >= 0 and done[select] == 0 and select != extra1 and select != extra2:
            total -= mark
            marks[select] = mark
            done[select] = 1
    return total

def adjust(marks,total,questions):
    for i in range(questions):
        if total > 0:
            if i < 6 and str(marks[i]).isdigit():
                diff = 2 - marks[i]
                if total - diff >= 0:
                    marks[i] = 2
                    total -= diff
                else:
                    marks[i] += total
                    total = 0
            elif i < 10 and str(marks[i]).isdigit():
                diff = 5 - marks[i]
                if total - diff >= 0:
                    marks[i] = 5
                    total -= diff
                else:
                    marks[i] += total
                    total = 0
        else:
            break

questions = 10

total = str(infile.readline())
while total != '-1':
    marks = [" "] * questions
    done = [0] * questions
    if total.isalpha():  # This is line 66
        outfile.write("A," * (questions - 1))
        outfile.write("A" + "\n")
    else:
        total_marks = int(total)
        total = assign2m(marks,done,int(total))
        if int(total) > 0:
            total = assign5m(marks,done,int(total))
        if int(total) > 0:
            adjust(marks,int(total),questions)
    total = str(infile.readline())
    print(marks,total_marks)
    print(total, type(total))

infile.close()
outfile.close()

And this is my input txt file content:

12
2
13
12
9
16
10
6
20
8
6
5
10
5
13
5
9
5
14
14
8
8
9
9
13
A
10
9
10
12
18
13
9
20
16
14
7
3
11
5
8
9
17
8
11
12
13
8
8
16
4
8
1
9
13
17
19
10
6
18
9
15
12
5
4
8
8
16
15
7
-1

Problem occurs when it reads the character 'A' .

Answer 1

isalpha checks if every character of the string is alphabetic. Since your string contains a newline character \\n , total.isalpha() returns False . You can strip the whitespace with

total = str(infile.readline()).strip()