Python: ValueError: I/O operation on closed file. Input/Output Lab

Question

In my Python lab, I need to ask the user how many numbers to store; have them enter said numbers individually and store them in a file named numbers1.txt. Then again, repeat this process but store the numbers in a file named numbers2.txt. From there I had to write some code that would read a line from one file and a line from the other file, the 2 integers are multiplied together and their value is added to a variable called scalar_product which was initialized at 0. The code should stop when one of the files has reached end of file.

The code I have so far is as follows:

 def main():
    num = int(input("How many numbers would you like to store"))
    numbers1 = open('numbers1.txt', 'w')
    for count in range(1, num + 1):
        nums = input("Enter each number individually {}:".format(count))
        numbers1.write(str(nums) + "\n")

    numbers1.close()

def main_two():
    num2 = int(input("How many numbers would you like to store"))
    numbers2 = open('numbers2.txt', 'w')
    for count in range(1, num2 + 1):
        nums2 = input("Enter each number individually {}:".format(count))
        numbers2.write(str(nums2) + "\n")

    numbers2.close()


main()
main_two()


numfile1 = open("numbers1.txt","r")
numfile2 = open("numbers2.txt","r")
scalar_product = 0
number1 = numfile1.readline()
number2 = numfile2.readline()
while number1 != "" and number2 != "":
    scalar_product += int(number1) * int(number2)
    number1 = numfile1.readline()
    number2 = numfile2.readline()
    numfile1.close()
    numfile2.close()

I have no issues with the first few steps, Python prompts the users for the amount of numbers they would like to store but when I reach the section on multiplying the 2 values from numbers1.txt and numbers2.txt I get the following ValueError:

 How many numbers would you like to store2
Enter each number individually 1:4
Enter each number individually 2:5
How many numbers would you like to store3
Enter each number individually 1:4
Enter each number individually 2:6
Enter each number individually 3:3
Traceback (most recent call last):
  File "/Users/jake./PycharmProjects/CH9_Munyak_Jacob/ReadingProcessFiles.py", line 31, in <module>
    number1 = numfile1.readline()
ValueError: I/O operation on closed file.

Process finished with exit code 1

Can anybody point me in the right direction?

I am not sure why It's a closed file when I re-opened it in line 24 and line 25

0x0fba · Accepted Answer · 2022-11-23 14:21:10Z

1

Files must keep open in the loop while reading.

while number1 != "" and number2 != "":
    scalar_product += int(number1) * int(number2)
    number1 = numfile1.readline()
    number2 = numfile2.readline()

# close files at the end
numfile1.close()
numfile2.close()

answered Nov 23, 2022 at 14:21

0x0fba

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Comments

chepner · Accepted Answer · 2022-11-23 14:18:43Z

You are closing the files too soon. The calls to close should be after the loop, not in the loop, but you should be using a with statement to open the files so that they will be closed automatically once you are done with them.

Using zip to create a single iterator that reads from both files in parallel is also a good idea.

scalar_product = 0
with open("numbers1.txt") as numfile1, open("numbers2.txt") as numfile2:
    for number1, number2 in zip(numfile1, numfile2):
        scalar_product += int(number1) * int(number2)

You can shorten this even more by using a single generator expression to sum up all the products.

with open("numbers1.txt") as numfile1, open("numbers2.txt") as numfile2:
    scalar_product = sum(int(x) * int(y) for x, y in zip(numfile1, numfile2))

Ammar_Asim_23 · Accepted Answer · 2022-11-23 14:54:43Z

0

#This will be a quick fix for your problem
with open("numbers1.txt") as numfile1:
    with open("numbers2.txt", "r") as numfile2:
        scalar_product = 0
        number1 = numfile1.readline()
        number2 = numfile2.readline()
        while number1 != "" and number2 != "":
            scalar_product += int(number1) * int(number2)
            number1 = numfile1.readline()
            number2 = numfile2.readline()

answered Nov 23, 2022 at 14:54

Ammar_Asim_23

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1 Comment

AlexK Over a year ago

Please don't post only code as answer, but also provide an explanation what your code does and how it solves the problem of the question. Answers with an explanation are usually more helpful and of better quality, and are more likely to attract upvotes.

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