ValueError: could not convert string to float: '' fron Entry Widget

[russellm44]

Sorry i didnt include a sample as I didnt think it would help as you cant see the problem as such, as it happens when you select the contents of entry and type a new value. The code I have used I have replicated from others and videos as I am just starting out with python.

I have included a simple example of what I was doing that replicates the issue.

if I run this program and focus is set on the entry field and then type a number, in this example I pressed the number '6' the stringvar is updated twice, first with '' and i get the ValueError: could not convert string to float: '' and then as I would expect it is updated with '6'.

My program would only ever need positive numbers entered but the way I was doing it I now see was wrong

I have now updated my code now to reflect the way you have shown with a class and try/except and it works thank you.

However I am still interested to know why '' is being passed when I type '6' if youre able to shed any light on this?

Thanks for your help.

This is the sample code

import tkinter as tk

root = tk.Tk()

txt1 = tk.StringVar()
txt1.set("0")

def check(*args):
    print(f'*{type(txt1.get())} - {txt1.get()}*')

entr1 = tk.Entry(root, textvariable=txt1)
entr1.place(x=20,y=20)

txt1.trace_add("write", check)

root.mainloop()

Output:
*<class 'str'> - *
*<class 'str'> - 6*

deanhystad write Mar-05-2024, 09:09 PM:
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