Lambda Variable Assignment (for Tkinter command callbacks)

Question

I was trying to learn a bit more about Tkinter and came across this code online

import Tkiner
import ttk
root = Tk()
l =ttk.Label(root, text="Starting...")
l.grid()
l.bind('<Enter>', lambda e: l.configure(text='Moved mouse inside'))
l.bind('<Leave>', lambda e: l.configure(text='Moved mouse outside'))
l.bind('<1>', lambda e: l.configure(text='Clicked left mouse button'))
l.bind('<Double-1>', lambda e: l.configure(text='Double clicked'))
l.bind('<B3-Motion>', lambda e: l.configure(text='right button drag to %d,%d' % (e.x, e.y)))
root.mainloop()

When I ran this program, and dragged my mouse over the screen while the RMB was pressed it gave me the coordinates as is mentioned it should do in the "B3-Motion" bind.

What exactly does the temp variable "e" refer to in this scenario?

Thanks!

It's just the first argument to the function − in this case the event that Tkinter sends when you click a button. — Martin Tournoij
– Martin Tournoij, Commented Mar 25, 2016 at 14:45

Bryan Oakley · Accepted Answer · 2016-03-25 15:29:20Z

2

When you bind a function to an event with widget.bind(...), tkinter will always pass in an argument to the function that represents the event when it calls the function. Typically this is named event, but sometimes abbreviated as e.

The event object has information about the event, such as which widget received the event, the x/y coordinate of the cursor when the event occurred, and other useful information.

You can read a bit more about that object here: http://effbot.org/tkinterbook/tkinter-events-and-bindings.htm .

answered Mar 25, 2016 at 15:29

Bryan Oakley

389k53 gold badges582 silver badges739 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Sharpfawkes Over a year ago

Thanks a lot for the help :D

Collectives™ on Stack Overflow

Lambda Variable Assignment (for Tkinter command callbacks)

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related