Adding and saving to list in external json file

I’m very new to Python and I’m struggling when it comes to saving the data that the user has entered to a json file when quitting the application. Also every time I run my code all the data inside the json file is wiped. When I enter the input to save and exit I get this error code:

Traceback (most recent call last):
  File "C:\Users\User\Downloads\sit_resources\sit_resources\sit_admin_application.py", line 86, in <module>
    main_menu()
  File "C:\Users\User\Downloads\sit_resources\sit_resources\sit_admin_application.py", line 23, in main_menu
    save()
  File "C:\Users\User\Downloads\sit_resources\sit_resources\sit_admin_application.py", line 82, in save
    patients_file.write(finallist)
io.UnsupportedOperation: not writable

Here is my code below:

import json
patients_file = open("patients.json", "r")
loaded_patients = json.load(patients_file)

def main_menu():
    '''Function docstring documentation here'''
    print("\nSIT Data Entry Menu")
    print("==========================")
    print("1: Print Patients' List\n2: Add Patient\n3: Delete Patient\n4: Exit")
    print("==========================")
    input1 = input("Enter your menu selection:")
    if input1 == "1":
        patients_list()
    elif input1 == "2":
        add_patient()
    elif input1 == "3":
        remove_patient()
    elif input1 == "4":
        save()
    else:
        print ("Please enter a valid input")
        main_menu()

def patients_list():
    print("\nSIT current patients:\n")
    loaded_patients.sort(key=str.casefold)
    for number, item in enumerate(loaded_patients, start=1):
        print(number, item)
    print("\nTotal number of registered patients is", len(loaded_patients))
    main_menu()

def add_patient():
    newpatient = input("\nEnter new Patient -> Lastname Firstname:")
    print ("Do the details you have entered look correct? y/n")
    confirm = input()
    if confirm == "y":
        loaded_patients.append(newpatient)
        print ("Patient successfully added to list")
        main_menu()
    elif confirm == "n":
        print ("Patient import cancelled")
        add_patient()
    else:
        print ("Please enter a valid input")
        add_patient()

def remove_patient():
    print ("Which of the following patients would you like to remove?")
    loaded_patients.sort(key=str.casefold)
    for number, item in enumerate(loaded_patients, start=1):
        print(number, item)
    try:
        removepatient = int(input("\nEnter the number of the patient you would like to remove"))
        print ("Does the patient number you have entered look correct? y/n")
        delconfirm = input()
        if delconfirm == "y":
            try:
                removepatient = (removepatient - 1)
                loaded_patients.pop(removepatient)
                print ("Patient was successfully removed from the list")
                main_menu()
            except IndexError:
                print("Please enter a valid input")
                remove_patient()
        elif delconfirm == "n":
            print ("Deletion cancelled")
            remove_patient()
        else:
            print ("Please enter a valid input")
            remove_patient()
    except ValueError:
        print ("Please enter a valid input")
        remove_patient()

def save():
    open("patients.json", "w")
    finallist = json.dumps(loaded_patients)
    patients_file.write(finallist)
    print("Patient List successfully saved")
    quit()

main_menu()

I store the json file in the same directory and all it contains is a list:

["Soreback Leigh", "Neckache Annette", "Sorefoot Jo", "Kaputknee Matt", "Brokentoe Susan", "Tornligament Alex"]

If anyone could help me out and let me know what I’m doing wrong or any simpler method I could use, it would be greatly appreciated.
Thanks

>Solution :

You are trying to write to patients_file, which you opened in read-only mode.