Editing a text file based on user input error. When the user adds an entry I get the this error – 'str' object does not support item assignment

Creating a program where the user can edit entries in a text file (couriers). However, when writing to the file I get the above error and I’m not too sure as to what exactly is going on here.

Couriers.txt

Ups
Fedex

Couriers.py

CourierList= []

with open('couriers.txt','r+') as file:
    for courier in file:
        CourierList.append(courier.strip())

#Prints the list with the key value#
for i in range(len(CourierList)):
    print (i, end = " ")
    print (CourierList[i])

print("")

UserInput = int(input("Which courier (number) would you like to update: "))
ChangeInput = input("What would you like to change it to?: ")    

CourierList = CourierList[UserInput]=ChangeInput <--- ERROR IS HERE

file.write(CourierList)

file.close()

I can get the new entry into the list created, but when writing it back to the file I get the issue.

Thank you for nay help!

>Solution :

First of all, you have to replace

CourierList = CourierList[UserInput]=ChangeInput

by

CourierList[UserInput] = ChangeInput

Then you need this to write your updated list to file line by line:

with open('couriers.txt', 'w') as file:
    for item in CourierList:
        file.write("%s\n" % item)

Full code:

CourierList = []

with open('couriers.txt', 'r+') as file:
    for courier in file:
        CourierList.append(courier.strip())

for i in range(len(CourierList)):
    print(i, end=" ")
    print(CourierList[i])

print("")

UserInput = int(input("Which courier (number) would you like to update: "))
ChangeInput = input("What would you like to change it to?: ")    

CourierList[UserInput] = ChangeInput

with open('couriers.txt', 'w') as file:
    for item in CourierList:
        file.write("%s\n" % item)