CODEWITHSUNDEEP
pythontkinterwidgettkinter-entry
paddypantsonfire
paddypantsonfire

Reputation: 41

clearing an entry widget box

I want to use an entry widget to get a number between 1 and 9. If any other key is pressed I want to remove it from the display.

    def onKeyPress(event):
        if event.char in ['1', '2', '3', '4', '5', '6', '7', '8', '9']
            ...do something
            return

        # HERE I TRY AND REMOVE AN INVALID CHARACTER FROM THE SCREEN
        # at this point the character is:
        #   1) visible on the screen
        #   2) held in the event
        #   3) NOT YET in the entry widgets string
        # as the following code shows...
        print ">>>>", event.char, ">>>>", self._entry.get()
        # it appeARS that the entry widget string buffer is always 1 character behind the event handler

        # so the following code WILL NOT remove it from the screen...
        self._entry.delete(0, END)
        self._entry.insert(0, "   ")

    # here i bind the event handler    
    self._entry.bind('<Key>',  onKeyPress)

OK so how can I clear the screen?

Upvotes: 2

Views: 1027

Answers (3)

user2155059
user2155059

Reputation: 151

a simple way to clear the entry widget is:

from tkinter import *

tk = Tk()


# create entry widget

evalue = StringVar()
e = Entry(tk,width=20,textvariable=evalue)
e.pack()


def clear(evt):
    evalue.set("")   # the line that removes text from Entry widget

tk.bind_all('<KeyPress-Return>',clear)  #clears when Enter is pressed
tk.mainloop()

you can use this in whatever context you wish, this is just an example

Upvotes: 0

Jdog
Jdog

Reputation: 10721

import Tkinter as tk

class MyApp():
    def __init__(self):
        self.root = tk.Tk()
        vcmd = (self.root.register(self.OnValidate), 
                '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')
        self.entry = tk.Entry(self.root, validate="key", 
                              validatecommand=vcmd)
        self.entry.pack()
        self.root.mainloop()

    def OnValidate(self, d, i, P, s, S, v, V, W):
        # only allow integers 1-9
        if P == "":
            return True
        try:
            newvalue = int(P)
        except ValueError:
            return False
        else:
            if newvalue > 0 and newvalue < 10:
                return True
            else:
                return False

app=MyApp()

Taken from this answer with modified validation to only allow integers 1-9.

(I'm sure there is a better way to write that validation but it does the job as far as I can see.)

Upvotes: 0

Bryan Oakley
Bryan Oakley

Reputation: 385900

The way you are going about input validation is wrong. What you ask can't be done with the code you've posted. For one, as you've discovered, when you bind on <<Key>>, by default that binding fires before the character is present in the widget.

I could give you workarounds, but the right answer is to use the built-in facilities for input validation. See the validatecommand and validate attributes of the entry widget. This answer to the question Interactively validating Entry widget content in tkinter will show you how. That answer shows how to validate against upper/lower, but it's easy to change that to compare against a set of valid characters.

Upvotes: 1

Related Questions