How do I make Bind and Command do the same thing in tkinter?

Question

I have a tkinter GUI with an entry field and a validation button. I'd like to call the same function when I press a key in the entry, or when I click the button.

The problem is, with the bind method on the entry, I need a "self" argument for my function to work, but not with the button.

Here is the simplified code:

from tkinter import *
import tkinter.messagebox
import tkinter.filedialog


def function():
    print("Here are some words.")

my_window = Tk()

text = StringVar()
input_widget = Entry(my_window, textvariable = text) #We create an input widget.
input_widget.bind("<Return>", function)

benjamin = Button(my_window, text ='Print', command = function) #We create another widget, a 
# button that sends the same function as pressing <Return> key.

input_widget.grid(row = 0, column = 0) #We use grid to place our widgets.
benjamin.grid(row = 0, column = 1)


my_window.mainloop()

With this code, when I use the button, no problem, it prints, but when I use the bind, it returns:

Exception in Tkinter callback
Traceback (most recent call last):
File "C:\"blablabla"\tkinter\__init__.py, line 1533, in __call__
    return self.func(*args)
TypeError: function() takes 0 positionnal arguments but 1 was given

I can make it work by calling two functions one for the button, and another for the entry with a self argument:

def function2(self):
    print("It works with this function.")

Is there any way to make both .bind and command share the the same function?

Answer 1

Add this to your binding:

input_widget.bind("<Return>", lambda event: function())

Event bindings all require an event parameter which is automatically passed to the function. By using a lambda with the parameter event; you can take in this "event" variable and basically discard it and do whatever is in function()

Answer 2

You could write your function so that it takes any number of arguments:

def function(*args):
    #args is now a tuple containing every argument sent to this function
    print("Here are some words.")

Now you can successfully call the function with 0, 1, or any other number of arguments.

---

Alternatively, you could keep your function as it is, and use a lambda to discard the unused self value:

input_widget.bind("<Return>", lambda x: function())