Python tkinter disable the button until all the fields are filled

Tkinter variables have a method called trace to add an observer, so the callback function is called when the value changes. I think it is much more efficient than root.bind("<Enter>", myfunction):

import Tkinter as tkroot = tk.Tk()def myfunction(*args):    x = var.get()    y = stringvar1.get()    z = stringvar2.get()    if x and y and z:        button.config(state='normal')    else:        button.config(state='disabled')stringvar1 = tk.StringVar(root)stringvar2 = tk.StringVar(root)var = tk.StringVar(root)stringvar1.trace("w", myfunction)stringvar2.trace("w", myfunction)var.trace("w", myfunction)entry1 = tk.Entry(root, width=15, textvariable=stringvar1)entry1.grid(row=1,column=1)entry2 = tk.Entry(root, width=15, textvariable=stringvar2)entry2.grid(row=1,column=2)choices = ('a','b','c')option = tk.OptionMenu(root, var, *choices)option.grid(row=1,column=3)button = tk.Button(root,text="submit")button.grid(row=1, column=4)root.mainloop()

What about validate and validatecommand properties of Entry ?

#!/usr/bin/env python3import tkinterclass App:    def __init__(self):        self.root = tkinter.Tk()        self.variables = {}        self.entries = {}        self.vcmd = (self.root.register(self.observer), '%W', '%P')        self.make_entry('fname')        self.make_entry('sname')        self.make_submit_button('Send')    def make_entry(self, name):        self.variables[name] = tkinter.StringVar()        self.entries[name] = tkinter.Entry(            self.root,            textvariable=self.variables[name],            validate='all',            validatecommand=self.vcmd)        self.entries[name].pack(side=tkinter.TOP)    def make_submit_button(self, text):        self.submit_button = tkinter.Button(            self.root,            text=text,            state=tkinter.DISABLED)        self.submit_button.pack(side=tkinter.BOTTOM)    def observer(self, id_, value):        id_ = int(id_[1:])        self.update_submit_button_state(entry_exclude=(value and id_ or None))        return True    def update_submit_button_state(self, entry_exclude=None):        if all(            var.get()             for name, var in self.variables.items()            if id(self.entries[name]) != entry_exclude        ):            self.submit_button.config(state=tkinter.NORMAL)        else:            self.submit_button.config(state=tkinter.DISABLED)App().root.mainloop()

Try this:

import Tkinter as tkroot = tk.Tk()def myfunction(*event):    x=var.get()    y=entry1.get()    z=entry2.get()    print len(x),":",len(y),":",len(z)    if len(y)>0 and len(x)>0 and len(z)>0:        button.config(state='normal')    else:        button.config(state='disabled')entry1=tk.Entry(root,width=15)entry1.grid(row=1,column=1)entry2=tk.Entry(root,width=15)entry2.grid(row=1,column=2)choices=('a','b','c')var=tk.StringVar(root)option=tk.OptionMenu(root,var,*choices)option.grid(row=1,column=3)button=tk.Button(root,text="submit")button.grid(row=1,column=4)button.config(state='disabled')root.bind_class("Entry","<FocusOut>",myfunction)var.trace('w', myfunction)root.mainloop()