my programme gives me errors if I choose menu option 3 without doing menu option 2 first

Question

This is my function for menu option 3, I think it isn't working because it'suppose to use info from option 2 to create new routes. But I would like to be able to still choose option 3 and just display a message that "no way points are available to create a route" if option 2 isn't chosen.

def menu3(waypoints, routes):
    try:
        num = int(input("How many routes would you like to create: "))
        for i in range(0,num):
            name = input("Enter route name: ")
            routes[name] = waypoints

            answer = ''
            new_route = False
            while answer != 'y' or answer != 'Y' or answer != 'n' or answer != 'N':
                answer = input("\nWould  you like to view your new route? (Y/N): ")
                if answer == 'y' or answer == 'Y':
                        name = input("Enter route name: ")
                        for key in routes.keys():
                            if key == name:
                                print(routes[key])
                                new_route = True
                        if new_route == False:
                            print("The route has not been saved or created.")
                        break

                elif answer == 'n' or answer == 'N':
                    break
                Error()
    except ValueError as e:
        print("Error no Waypoints available to create new route")

and here is where I call it below

elif choice == 3:
        menu3(waypoints, routes)

And my error is

File "C:/Users/Daniel/PycharmProjects/Assignment2/assignment2.4.py", line 102, in <module>
    main()
File "C:/Users/Daniel/PycharmProjects/Assignment2/assignment2.4.py", line 94, in main
    menu3(waypoints, routes)
UnboundLocalError: local variable 'waypoints' referenced before assignment`

Here's where settings are set:

def main():
    choice = 0
    location = []
    routes = {}
    while 1 == 1:
        print("\nMENU")
        print("********************************************************")
        print("*1:\tCurrent location. (Current location saved as waypoint)")
        print("*2:\tSelect to enter Waypoint(s)")
        print("*3:\tCreate Paths using the waypoints you have saved")
        print("*4:\tCalculate the distance to a waypoint from the current location")
        print("*5:\tCalculate the direction as a compass bearing from the current location to a given waypoint.")
        print("*6:\tExit program.")
        print("*********************************************************")
        try:
            choice = int(input("Option: "))
        except ValueError as error:
            Error()
            print(error)
        if choice == 1:
           location = menu1()
        elif choice == 2:
            waypoints = []
            waypoints = menu2(waypoints)
        elif choice == 3:
            menu3(waypoints, routes)

        elif choice == 6:
            break
        else:
            print("Please enter a valid option.")

       if __name__ == "__main__":
                 main()

Answer 1

"local variable 'waypoints' referenced before assignment" means waypoints doesn't exist yet. If you check your code, you're creating the variable when selecting the option 2:

elif choice == 2:
    waypoints = []   # <---- here is the declaration.

Just add the declaration in before the while.

def main():
    choice = 0
    location = []
    routes = {}
    waypoints = []      # < --- Declaration
    while 1 == 1:
        print("\nMENU")
        ...

if __name__ == "__main__":
    main()

Answer 2

You need to define waypoints in your main method. Your main should look something like this - now when you call menu3(waypoints, routes) before choosing option 2, waypoints will have been assigned a value:

def main():
    choice = 0
    location = []
    routes = {}
    waypoints = []
    while 1 == 1:
        print("\nMENU")
        print("********************************************************")
        print("*1:\tCurrent location. (Current location saved as waypoint)")
        print("*2:\tSelect to enter Waypoint(s)")
        print("*3:\tCreate Paths using the waypoints you have saved")
        print("*4:\tCalculate the distance to a waypoint from the current location")
        print("*5:\tCalculate the direction as a compass bearing from the current location to a given waypoint.")
        print("*6:\tExit program.")
        print("*********************************************************")
        try:
            choice = int(input("Option: "))
        except ValueError as error:
            Error()
            print(error)
        if choice == 1:
           location = menu1()
        elif choice == 2:
            waypoints = [] # I left this because I assume you want to pass menu2 an empty list
            waypoints = menu2(waypoints)
        elif choice == 3:
            menu3(waypoints, routes)

        elif choice == 6:
            break
        else:
            print("Please enter a valid option.")

       if __name__ == "__main__":
             main()

To check for this value in menu3(), you can do something like this:

def menu3(waypoints, routes):
    if waypoints:
        num = int(input("How many routes would you like to create: "))
        for i in range(0,num):
            name = input("Enter route name: ")
            routes[name] = waypoints

            answer = ''
            new_route = False
            while answer != 'y' or answer != 'Y' or answer != 'n' or answer != 'N':
                answer = input("\nWould  you like to view your new route? (Y/N): ")
                if answer == 'y' or answer == 'Y':
                        name = input("Enter route name: ")
                        for key in routes.keys():
                            if key == name:
                                print(routes[key])
                                new_route = True
                        if new_route == False:
                            print("The route has not been saved or created.")
                        break

                elif answer == 'n' or answer == 'N':
                    break
                Error()
    else:
        print("Error no Waypoints available to create new route")