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

[deanhystad]

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.

Code is useful for a lot of things. It is a very accurate description of the problem. It provides insight into you level of knowledge. It establishes a starting point for future conversations. It is best if you can post code that others can run to see the problem.

import tkinter as tk

def check(*args):
    print(float(txt1.get()))

root = tk.Tk()
txt1 = tk.StringVar(root, "0")
txt1.trace_add("write", check)
entr1 = tk.Entry(root, width=10, textvariable=txt1)
entr1.pack(padx=50, pady=50)
root.mainloop()

And then add instructions for how to make the error occur.

To make the error happen, select the text in the entry and type in a digit. You should get an error like this:

Error:
  File "..test.py", line 4, in check
    print(float(txt1.get()))
ValueError: could not convert string to float: ''

To answer your question, you get "" because pasting (or typing) in an entry deletes any selected text before entering new text. When there is a selection, the entry gets written twice. You'll see this if you run your example and alternate between typing with or without selecting text in the entry.