python - Calling a method with an event handler -

why, if put "normal" call method button1click() in bind call, program not start? removing parenthesis problem solved. i'm using program reference: thinking in tkinter

also, why should add event argument button1click() method?

from tkinter import * class myapp:     def __init__(self, parent):         self.myparent = parent          self.mycontainer1 = frame(parent)         self.mycontainer1.pack()          self.button1 = button(self.mycontainer1)         self.button1.configure(text="ok", background= "green")         self.button1.pack(side=left)         self.button1.bind("<button-1>", self.button1click) # <--- no () !      def button1click(self, event):         self.button2 = button(self.mycontainer1, text="lol")         self.button2.bind("<button-1>", self.button1click)         self.button2.pack()  root = tk() myapp = myapp(root) root.mainloop() 

bind() expects callable , expects argument.

if pass self.button1click(), pass none, because returned call.

as call performed clickable object, not supposed call yourself.

so, next step: pass self.button1click, , clock button. given "thing" tried called event object argument, fails, because method not prepared that.

so have 2 options:

• either modify method can called event object, such def button1click(self, event):,
• or wrap in lambda call: lambda event: self.button1click().

in latter case, give bind() method callable accepts 1 argument, , call wanted @ time of calling (thus ()).