Is there any possibility to use lists globally?

Question

I have an function for clearing a list and a the ame time copying it. I need the copy outside of the function, but when I use "global" there is only an empty list. The list is not empty inside of the function, only outside. What can I do?

k_grade_list = []
g_grade_list = []

def average():
    g_grade = input_one.get()
    k_grade = input_two.get()
    wert = int(input_three.get())

    g_grade_list.extend(g_grade.split(','))
    g_grade_avg = float((summe(g_grade_list) / len(g_grade_list)))

    k_grade_list.extend(k_grade.split(','))
    k_grade_avg = float((summe(k_grade_list) / len(k_grade_list)))

    wert = wert / 100

    return (k_grade_avg * wert) + (g_grade_avg * (1 - wert))


def list_clear():
    global ks_grade_list
    ks_grade_list = k_grade_list
    global gs_grade_list
    gs_grade_list = g_grade_list

    k_grade_list.clear()
    g_grade_list.clear()

You're making them empty with `clear()`. Note that you're emptying both `ks_grade_list` and `k_grade_list`, since both variables are references to the same list. — Barmar, May 22 '20 at 19:55
How can I fix this? Is there any possibility for not making both lists empty? @Barmar — Gümmi, May 22 '20 at 20:03
See https://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list — Barmar, May 22 '20 at 20:04
I don't understand what you're trying to do. What is the purpose of `ks_grade_list` and `gs_grade_list`? You never use them anywhere. — Barmar, May 22 '20 at 20:06

score 1 · Answer 1 · answered May 22 '20 at 19:53

1

You have to define the list outside of the function and reference it using global like this:

k_grade_list = []
g_grade_list = []

// Do stuff with the list

def list_clear():
    global k_grade_list, g_grade_list

    k_grade_list.clear()
    g_grade_list.clear()

answered May 22 '20 at 19:53

Vincent

482
4
15

Assigning it after declaring it global should have the same effect. – Barmar May 22 '20 at 19:54
Sorry, so the lists are already defined and filled with inputs from tkinter. – Gümmi May 22 '20 at 19:55
You can put the empty initialization at the beginning of the program regardless. – Vincent May 22 '20 at 19:56
´´´g_grade = input_one.get() k_grade = input_two.get() g_grade_list.extend(g_grade.split(',')) k_grade_list.extend(k_grade.split(','))´´´ – Gümmi May 22 '20 at 19:57

score 0 · Answer 2 · answered May 22 '20 at 20:08

Don't use clear(), since that modifies the list that both variables reference. Just assign empty lists to the variables, this will make new lists.

def list_clear():
    global ks_grade_list
    ks_grade_list = k_grade_list
    global gs_grade_list
    gs_grade_list = g_grade_list

    k_grade_list = []
    g_grade_list = []

Is there any possibility to use lists globally?

2 Answers2