A list is whipped everytime I run the program

I'm trying to write a program that will take user input and store it to a list, the user can input the number 3 to add a new item and enter 1 to display all previous items.

The code I wrote:

bigList = []
def reminder():
    Input = input("Reminder Menu:\n 1. show all reminders \n 2. search Reminders\n 3. Add Reminders \n 4. Modify Reminders \n 5. Export Reminder \n 6. Exit\n \n")
    if Input == "3":
        newInput = input("please enter a reminder \n")
        item1 = item(newInput)

    bigList.append(item1)
    for i in bigList:
        print(i)
    Input = input("Reminder Menu:\n 1. show all reminders \n 2. search Reminders\n 3. Add Reminders \n 4. Modify Reminders \n 5. Export Reminder \n 6. Exit\n \n")

    if Input == "1":
        print(bigList)

reminder()

This is the "item" class that I created:

class item:
    def __init__ (self, userInput):
        self.userInput = userInput

It will run and append the user input into the bigList but if I run it again, the list will be empty and the new user input will be the only one in the list. What is wrong here?