String Index Out Of Range - Even With Append and Initializing With * 1000 - Python

Question

This is one my very first python programs, and my very first Tkinter program, so it is just a test.

What I am hoping to accomplish is getting an array (a[]) to store a number from dataA through the variable g at the location a[f].

Then I want to be able to choose which two locations (a[b] and a[c]) that get added up to the variable d, which will be displayed on the widget "prompt".

from tkinter import *
from tkcalendar import *
from array import *
root = Tk()
i = 0



def getDateA():
    a = array('b',[]*10000)
    global i
    f = i + 1
    c = int(dataC.get())
    b = int(dataB.get())
    g = dataA.get()
    a.append(g[f])
    d = int(a[b]) + int(a[c])
    
    prompt.configure(text = d)
    
    
dataA = Entry(root, text="Enter a", width = 20)
dataA.grid(column = 2)

dataB = Entry(root, text="Enter b", width = 20)
dataB.grid(column = 3)

dataC = Entry(root, text="Enter c", width = 20)
dataC.grid(column = 4)

my_button = Button(root, text="get date", command=getDateA)
my_button.grid(column = 2)

prompt = Label(root, text="Ingenting")
prompt.grid(column=1)
root.mainloop()

At first, the array wasn't long enough, so I added append, but I still got the error message (at the bottom of this post).

Then I initialized and - hopefully - added 10000 empty indexes. Still, I get the following error message:

Exception in Tkinter callback Traceback (most recent call last):
File "C:\Python38\lib\tkinter_init_.py", line 1883, in call return self.func(*args) File "Linear algebra.py", line 16, in getDateA a.append(g[f]) IndexError: string index out of range

Why is that?

What have you done to debug this? Have you examined `g` immediately before the error to see if it is what you expect it is? Same thing for `f`: is it what you're assuming it is? — Bryan Oakley, Sep 26 '20 at 22:30
`[]*10000` gives you 10000 repetitions of an empty list, which is still an empty list. You could try `[0]*10000` or `(0 for x in range(10000))` or `itertools.repeat(0, 10000)`. The latter two use less memory but the `range` one may be slower. See here for something similar: https://stackoverflow.com/a/35481867/3830997 — Matthias Fripp, Sep 27 '20 at 03:29

Mike67 · Answer 1 · 2020-09-27T11:58:48.750

I'm not sure what the purpose of this script is, but here are the changes to have it do something:

Make the array global so the array state is retained between updates
Initialize the array using [0], not []. The empty list does nothing.
g needs to be an int, not a string
Use a[i] to set the value instead of append
Increment i on each click to set the next value in the array

Here's the updated code:

from tkinter import *
from tkcalendar import *
from array import *
root = Tk()
i = 0
a = array('b',[0]*1000)  # global array, initialize all 0

def getDateA():
    global i,a
    f = i + 1
    c = int(dataC.get())  # convert all to ints
    b = int(dataB.get())
    g = int(dataA.get())
    a[i] = g  # set array element
    d = int(a[b]) + int(a[c])
    
    prompt.configure(text = d)
    i += 1  # update next spot in array
    
    
dataA = Entry(root, text="Enter a", width = 20)
dataA.grid(column = 2)

dataB = Entry(root, text="Enter b", width = 20)
dataB.grid(column = 3)

dataC = Entry(root, text="Enter c", width = 20)
dataC.grid(column = 4)

my_button = Button(root, text="get date", command=getDateA)
my_button.grid(column = 2)

prompt = Label(root, text="Ingenting")
prompt.grid(column=1)
root.mainloop()

Thank you for the help Mike, it did indeed work. But I have a question, why should I not use append? I would like to be able to have an index-printing prompt, to help keep track of all the values. But if I initialize 10000 empty spaces, this prompt would be infinitely long. — GeorgeWTrump, Sep 27 '20 at 10:42
You can use append if you prefer, just start with a zero length array. This may help with the index prompt also. — Mike67, Sep 27 '20 at 11:58

String Index Out Of Range - Even With Append and Initializing With * 1000 - Python

1 Answers1