Having the error "IndexError: list index out of range" in working with python, tkinter

Question

I'm new to python and I wanted to know why my program is not working. The error is "IndexError: list index out of range" for line 23 (This program is for my best friend's birthday that's tomorrow)

import datetime
import tkinter
from tkinter import *

t = Tk()
t.resizable(0, 0)
t.title("Sana's birthday!!!")
t.geometry('200x200')

current_date = datetime.date.today().strftime('%Y-%m-%d')
current_date_lst = current_date.split('-')

l1 = Label(t, text='Sana enter your birthday in yyyy-mm-dd format:').grid(row=1, column=1)
l2 = Label(t, text='Name of your birthday legend?:').grid(row=2, column=1)

b_date = tkinter.Entry(t)
b_date.grid(row=1, column=2)
name = tkinter.Entry(t)
name.grid(row=1, column=2)

b_date = b_date.get().split( '-' )

if current_date_lst[1] == b_date[1] and current_date_lst[2] == b_date[2]:
    age = int(current_date_lst[0]) - int(b_date[0])
    ordinal_suffix = {1: 'st', 2:'nd', 3:'rd', 11:'th', 12:'th', 13:'th'}.get(age % 10 if not 10<age<=13 else age % 14, 'th')
    print(f" It's {name}'s {age}{ordinal_suffix} Birthday!")
else:
    print('Sorry, today is not your birthday:(')

mainloop()

The error:

if current_date_lst[1] == b_date[1] and current_date_lst[2] == b_date[2]:
IndexError: list index out of range

ALai · Accepted Answer · 2021-07-14T14:02:34.460

There are two problems with your code:

When doing b_date.get().split( '-' ), no text has been entered on entry yet, so you always get an empty string, from here the IndexError
b_date and name have been both gridded on row 1, column 2. Thus, even if you think you are writing on b_date entry, you are actually writing on name entry.

Second problem is trivially solved by name.grid(row=2, column=2). To solve first problem, instead, you need to ensure entry is only read after some text has been written.

One possible solution: force user to push a button after having entered some text. An approach I like more: for each character entered, check if string is ok and do something if it is.

Here some sample code:

import datetime
import tkinter
from tkinter import *

t = Tk()
t.resizable(0, 0)
t.title("Sana's birthday!!!")
t.geometry('200x200')

current_date = datetime.date.today().strftime('%Y-%m-%d')
current_date_lst = current_date.split('-')

l1 = Label(t, text='Sana enter your birthday in yyyy-mm-dd format:').grid(row=1, column=1)
l2 = Label(t, text='Name of your birthday legend?:').grid(row=2, column=1)

b_date = tkinter.Entry(t)
b_date.grid(row=1, column=2)
name = tkinter.Entry(t)
name.grid(row=2, column=2)

t.bind("<KeyRelease>", lambda e: show_string(b_date, name))

def show_string(b_date, name):
    
    b_date = b_date.get().split( '-' )
    name = name.get()
    
    if len(b_date)==3:
        if current_date_lst[1] == b_date[1] and current_date_lst[2] == b_date[2]:
            age = int(current_date_lst[0]) - int(b_date[0])
            ordinal_suffix = {1: 'st', 2:'nd', 3:'rd', 11:'th', 12:'th', 13:'th'}.get(age % 10 if not 10<age<=13 else age % 14, 'th')
            print(f"It's {name}'s {age}{ordinal_suffix} Birthday!")
        else:
            print('Sorry, today is not your birthday:(')

mainloop()

What is happening:

You bind key pressed (actually key released, to ensure you are looking for the actual entered string) to a checker function show_string. See how to bind events to functions in tkinter, such as this answer
You split your string as usual
You ensure to only continue with your elaboration if string matches a given format. Trivial approach: ensure there are at least two "-" characters. Best approach: check if string is in format "yyyy-mm-dd"
Note that you were also printing name. You should print name.get() instead. Furthermore, you are printing it on the console, while you might be interested into updating a label in tkinter instead

Good luck and happy birthday to your friend

score 0 · Answer 2 · answered Jul 14 '21 at 13:16

So at this line in your program: b_date = b_date.get().split( '-' ) your GUI is not running, so b_date is likely an empty list.

You may need to add a Button to trigger the code which does this splitting, and testing.

Also note that any print() functions will print to the terminal and not on the GUI.

Having the error "IndexError: list index out of range" in working with python, tkinter

2 Answers2