How To Only Allow Certain Parameters Within An Entry Field On Tkinter

If i want an entry box in Tkinter that only accepts floating point numbers that are greater than or equal to 0.0 and less than or equal to 1.0 how would i do that?

Solution 1:

The proper way it to use tkinter's validate capabilities. But it's really a PIA to use.

dsgdfg has a good answer, but I can make that a lot neater, robust, and more dynamic:

import Tkinter as tk

classLimitedFloatEntry(tk.Entry):
    '''A new type of Entry widget that allows you to set limits on the entry'''def__init__(self, master=None, **kwargs):
        self.var = tk.StringVar(master, 0)
        self.var.trace('w', self.validate)
        self.get = self.var.get
        self.from_  = kwargs.pop('from_', 0)
        self.to = kwargs.pop('to', 1)
        self.old_value = 0
        tk.Entry.__init__(self, master, textvariable=self.var, **kwargs)

    defvalidate(self, *args):
        try:
            value = self.get()
            # special case allows for an empty entry boxif value notin ('', '-') andnot self.from_ <= float(value) <= self.to:
                raise ValueError
            self.old_value = value
        except ValueError:
            self.set(self.old_value)

    defset(self, value):
        self.delete(0, tk.END)
        self.insert(0, str(value))

You use it just like an Entry widget, except now you have 'from_' and 'to' arguments to set the allowable range:

root = tk.Tk()
e1 = LimitedFloatEntry(root, from_=-2, to=5)
e1.pack()
root.mainloop()

Solution 2:

If you want to call a button to check whether, this is a way to do it.

from tkinter import *

classGUI():
    def__init__(self, root):

        self.Entry_i = Entry(root, bd = 5)

        self.test = StringVar()
        Label_i = Label(root, textvariable = self.test)
        Button_i = Button(root, text = "Go", command = self.floatornot)

        self.Entry_i.grid()
        Label_i.grid()
        Button_i.grid()
        mainloop()

    deffloatornot(self):

        test = self.Entry_i.get()
        iffloat(test) < 0orfloat(test) > 1:
            self.test.set("Good")
        else: 
            self.test.set("")

root = Tk()
GUI(root)

The button will call the floatornot function. This will get the value of the entry and check if it okay or not. Depending on the result the value of the label will be changed.