return python function variable

Question

I have a function that returns several values, and I wanted to pass two of them out of the function, but when I try it returns that the variable outside the function has not been declared.

To illustrate in the code below, I would like the lists teste3 and teste4 of the function gerar_gráfico, to be used in the function index outside of the function gerar_graficos, remembering that it is a views of Django.

Function code:

class StorageData:
    list_shared = [] #lista compartilhada
    def __init__(self, *dados):
         self.list_shared.extend(dados) #inclui dados na lista

    def extend(self, *args):
         self.list_shared.extend(args)

    def reset(self):
        self.list_shared = [] #reseta lista caso queira zerar ela


def gerar_graficos(request):
    descricao = '01/02/2019 08:00'
    descricao2 = '01/02/2019 09:00'

    if request.method=='POST':
        descricao = request.POST['descricao']
        descricao2 = request.POST['descricao2']
    conn = cx_Oracle.connect('banco')
    cur = conn.cursor()

    cur.execute(consulta do banco)
    teste = []
    teste2 = []
    teste3 = []
    teste4 = []


    d = 0
    for line in cur:
        teste.extend(line)
    for indice, c in enumerate(teste):
        #if c + 0 == c:
            teste3.extend([c - 10000])
        #else:
            d = 0


    cur.execute(consulta do banco)
    for coluna in cur:
        teste2.extend(coluna)
    for indice2, c in enumerate(teste2):
        if indice2 >= d:
            teste4.extend([c])

    transfer = StorageData()
    transfer.reset()
    transfer.extend(teste3,teste4)

    width_n = 0.001
    bar_color = 'yellow'

    cur.close()
    conn.close()

    context = { 'descricao': descricao, 'descricao2': descricao2 }
    return render(request, 'core/graficos_list.html', context)

Code outside the function:

def index(request):
   trans = StorageData()
   my_list = trans.list_shared[0]
   my_list2 = trans.list_shared[1]
   fig = Figure()
   ax = fig.add_subplot(1,1,1)
   ax.plot(my_list, my_list2)
   #ax.bar(x_axis, y_axis, width=width_n, color=bar_color, align='center')
   ax.grid()
   buf = io.BytesIO()
   canvas = FigureCanvas(fig)
   canvas.print_png(buf)
   response=HttpResponse(buf.getvalue(), content_type='image/png')
   return (response)

Answer 1

It is not possible to access this way because descricao and descricao2 are valid variables only for the scope of the function gerar_graficos().

One solution would be to call these functions calcular_medida() and calcular_data() within the gerar_graficos() that if the x_axis and the y_axis are used in the template.

def gerar_graficos(request):
    descricao = '01/02/2019 08:00'
    descricao2 = '01/02/2019 09:00'

    if request.method=='POST':
        descricao = request.POST['descricao']
        descricao2 = request.POST['descricao2']


    y_axis = calcular_medida(descricao,descricao2)
    x_axis = calcular_data(descricao, descricao2)
    context = { 'descricao': descricao, 'descricao2': descricao2, 'x_axis' : x_axis, 'y_axis': y_axis }
    return render(request, 'core/graficos_list.html', context)

Another method would be to call a function in gerar_gráficos() to do what you want to do.

def gerar_graficos(request):
    descricao = '01/02/2019 08:00'
    descricao2 = '01/02/2019 09:00'

    if request.method=='POST':
        descricao = request.POST['descricao']
        descricao2 = request.POST['descricao2']


    calculaXY(descricao,descricao2)
    context = { 'descricao': descricao, 'descricao2': descricao2 }
    return render(request, 'core/graficos_list.html', context)

def calculaXY(descricao,descricao2):
    y_axis =  []
    x_axis = []
    y_axis = calcular_medida(gerar_graficos.descricao,gerar_graficos.descricao2)
    x_axis = calcular_data(gerar_graficos.descricao, gerar_graficos.descricao2)

I recommend giving a read on Class Based Views that can facilitate this whole question of attributes and functions.

Answer 2

@William, Dude from what I read in the comments, you need to get two different views to access the same data. You can try to store them in Ssion, such as:

 request.session['descricoes'] = [descrição, descricao2]

But this way I’m not 100% sure it will work, but it doesn’t cost to try. Now you can create a class to do this operation of storing shared data.

class StorageData:
    list_shared = [] #lista compartilhada
    def __init__(self, *dados):
         self.list_shared.extend(dados) #inclui dados na lista

    def reset(self):
        self.list_shared = [] #reseta lista caso queira zerar ela

Ready now to use it, just instantiate the class is pass your lists inside the constructor of it

StorageData (descrição, descricao2)

And when you want to use this data in another view just instantiate the class again without parameters and access the list_shared property.

#outra view para acessar os dados da descricao e descricao2
def sua_view(request):
    storage = StorageData()
    my_list = storage.list_shared # Aqui a propriedade irá retornar os mesmos dados que foi executado por outra instância passando os dados pelo construtor.

Try to make these ways and if it doesn’t work post there to see if there are other forms too.

Using: Here are two different views that will use the class

def transfer(request):

    transfer = Storage()
    transfer.reset() # Coloquei apenas para resetar a lista para cadastrar novamente os mesmos dados, para não ficar adicionando um monte de vez a cada requisição

    descricao = ["Esta lista é a decricao"]
    descricao2 = ["Esta lista é a decricao2"]
    transfer.extend(descricao,descricao2) # Aqui adiciona os dados na classe

    return render(request,'core/transfer.html',context{'descricao':descricao,'descricao2':descricao2})

def Transfer_get(request):
    trans = Storage()
    descricao = trans.list_shared[0]  # Aqui recupera os valores adicionados na classe
    descricao2 = trans.list_shared[1]

    return render(request, 'core/transfer2.html', context={'descricao':descricao,'descricao2':descricao2})

In the template I just showed the data

{{ descricao }}
{{ descricao2 }}

If you prefer you can pass the full list to the templates and it make the interaction in the list and display its data.

def Transfer_get(request):
    trans = Storage()
    lista = trans.list_shared  # Aqui recupera os valores adicionados na classe

    return render(request, 'core/transfer2.html', context={'lista':lista})

And in the template interact this list.

I also created the routes for these views. I made a simple change to the class by adding the extend method().

class Storage:

    list_shared = []

    def __init__(self, *args):
        self.list_shared.extend(args)

    def extend(self, *args):
        self.list_shared.extend(args)

    def reset(self):
        self.list_shared.clear()

Well tested here is the values pass normally to the two views, and if I add any more value in list_shared when you go to the list the new values also appear without problem. If you have done it right and see that there is no mistake and it still doesn’t work, post the code here the way you stayed to see if we can make some change or something.