What is the best way to perform a menu with submenus ( while with breaks or calling the menus in functions )?

Question

For a school project I need to have a menu with several submenus. What is the best way to approach this? I can put the menus inside whiles and give away break to those whiles when you want to go back to the previous one or separate the menus in functions and go calling when needed.

I do not know what would be the best option, I am open to suggestions, thanks in advance. for example

while 1:

# menu principal
existe()
print("========================")
print("     SA Airlines    ")
print("========================")
print("[1] - Adicionar")
print("[2] - Listar")
print("[3] - Procurar")
print(" ")
res = int(input("Opcao: "))

if res == 1:
    add.adicionar()
elif res == 2:

    while 1:

        # um menu secundario
        print("[1] - Aeronaves")
        print("[2] - Aeroportos")
        print("[3] - Rotas")
        print("[4] - Voltar")

        res = int(input("Opcao: "))
        if res == 1:
            listar.mostraAeronaves()
        elif res == 2:
            listar.mostraAeroportos()
        elif res == 3:
            listar.mostraRotas()
        elif res == 4:
            break;
        else:
            print("ERRO: A opção não se encontra defenida ! tente novamente!")

Answer 1

When they invented programming functions, it’s because they’re MUCH BETTER to organize the program and its contents - and this includes organizing the menu structure: you should not think that only the functionalities at the tips should be functions and that any code in the main body, either way, serves to do the menus.

If the menus all behave in the same way: have to display a list of options, pick a number and perform something else based on that number, the best thing you do is create a generic function to display these menus and the answer - and then you get the whole structure pre of the program very short and separate from the main logic:

aeronaves = []
aeroportos = []


def menu(titulo, opcoes):
    while True:
        print("=" * len(titulo), titulo, "=" * len(titulo), sep="\n")
        for i, (opcao, funcao) in enumerate(opcoes, 1):
            print("[{}] - {}".format(i, opcao))
        print("[{}] - Retornar/Sair".format(i+1))
        op = input("Opção: ")
        if op.isdigit():
            if int(op) == i + 1:
                # Encerra este menu e retorna a função anterior
                break
            if int(op) < len(opcoes):
                # Chama a função do menu:
                opcoes[int(op) - 1][1]()
                continue
        print("Opção inválida. \n\n")

def principal():
    opcoes = [
        ("Adicionar", adicionar),
        ("Listar", listar),
        ("Procurar", procurar)
    ]
    return menu("SA AIRLINES", opcoes)

def adicionar():
    opcoes = [
        ("Aeronaves", adicionar_aeronave),
        ("Aeroportos", adicionar_aeroporto),
        # ...
    ]
    return menu("Adicionar", opcoes)

def adicionar_aeronave():
    aeronaves.append(input("Nova aeronave: "))


def adicionar_aeroporto():
    aeroportos.append(input("Nova aeronave: "))

    #...

def listar():
   ...

def procurar():
   ...

principal()

I used an important feature of Python which is the possibility to pass functions as normal objects - that is, the "menu" function receives the functions themselves that should call, in each option, with parameters - and calls the appropriate functions in the line opcoes[int(op) - 1][1]().

The functions that use the menu define the options as a sequence of items with two other internal items: the first is the printable name of the option, and the second is the function itself, as an object. For this just put the name of the function without adding the ( ) that characterize the function call. (Otherwise Python simply calls the function unconditionally at that point and adds the value returned by it in the list of options)

Thus, the line opcoes[int(op) - 1][1]() "says" in item "op - 1" of the options , take the second item - which is the function itself (this we declare within the various functions that declare options to call the menu) and call this object as a function, without parameters.

Note that doing so, if tomorrow you decide to add a graphical interface for example instead of using prints and inputs, just redo the "menu" function and the whole structure of the program continues working normally.