I have been tasked on building a code using queues and a class in which you get three options:

1. Generates a new number
2. Calls on the first number of the queue and takes it out of the main queue(there is an auxiliary queue for that)
3. Shows the already called numbers

This is the class created:

class Fila:    
    def __init__(self):
        self._vet = []
    
    def enqueue(self, item): # enfileirar
        self._vet.append([-1])
    
    def dequeue(self): # desenfileirar
        self._vet.pop(0)

    def front(self): # mostrar o 1o da fila, sem remover!
        return(self._vet[1])
                
    def is_empty(self): # retorna se a fila esta vazia
        if len(self._vet) == 0:
            return True
        return False
        
    def __len__(self):
        return len(self._vet)

    def __str__(self): # representacao da fila como string
        return str(self._vet)

And this is the code I came up with:

from classeFila import *

if __name__ == "__main__":
    f1 = Fila()
    fAux = Fila()
    contador = 0

    while True:
        opcao = int(input("Digite 1 para obter nova senha, 2 para chamar próxima senha ou 3 para mostrar senhas chamadas."))

        if opcao == 1:
            contador  = 1
            f1.enqueue(contador)
            print("Sua senha é a de número", contador)
        elif opcao == 2:
            print("Senha número", f1[0], "está sendo chamada." )
            fAux.enqueue(f1[0])
            f1.dequeue()
        elif opcao == 3:
            print(fAux)
        else:
            print("Digite um número válido.")

The problem is, the moment I run the code and input option number 2, I get the error:

 Traceback (most recent call last):
 File "c:\\Users\\thoma\\Desktop\\Projetos Python\\Fahad\\Filas\\senhas.py", line 16, in \<module\>
 print("Senha número", f1\[0\], "está sendo chamada." )
 TypeError: 'Fila' object is not subscriptable

And while I get that the problem here is trying to use indexes, I've come short in terms of solutions as how I could specify which number is being called(f1[0] in "elif opcao == 2") without using indexing. Any guidance?

Tried taking out the index in the f1[0] mentioned above, and while the program could be run, the terminal would display "Senha número [-1, -1] está sendo chamada", or "Number [-1, -1] is being called", if you will.

CodePudding user response：

add __getitem__ function, this will allow you to use f1[0] in your code, this will get the element within f1 at the index of 0 from the internal _vet array read more here

class Fila:    
    def __init__(self):
        self._vet = []
    
    def enqueue(self, item): # enfileirar
        self._vet.append([-1])
    
    def dequeue(self): # desenfileirar
        self._vet.pop(0)

    def front(self): # mostrar o 1o da fila, sem remover!
        return(self._vet[1])
                
    def is_empty(self): # retorna se a fila esta vazia
        if len(self._vet) == 0:
            return True
        return False
        
    def __len__(self):
        return len(self._vet)

    def __str__(self): # representacao da fila como string
        return str(self._vet)

    def __getitem__(self, key): # this allows getting an element (overrided method)
        return self._vet[key]

CodePudding user response：

f1 is an object of class Fila and hence you can't write or use it as f1[0]