Tkinter and commands

[nihilium]

With a right click, a popup menu will appear, allowing to select from a list of colours. The queston is: is it necessary to create a callback function for each colour? How may I pass on information to the callback function?

Here's a short example script:

from Tkinter import *
 
root = Tk()
 
def colour():
    print 'Which colour was it?' 
# Here, the actual colour should've been printed instead!
 
# create a popup menu
menu = Menu(root, tearoff=0)
menu.add_command(label='Green', command=colour)
menu.add_command(label='Blue', command=colour)
 
# create a canvas
frame = Frame(root, width=128, height=128)
frame.pack()
 
def popup(event):
    menu.post(event.x_root, event.y_root)
 
frame.bind("<Button-3>", popup)
mainloop()
 

[YarrOfDoom]

This can be achieved by using lambda

command = lambda:colour("Blue")

However, when using this with 'bind', don't forget to make the lambda form accept the 'event'-argument so it can pass it on to your callback:

widget.bind("<sequence>", lambda ev: callback_function(ev, arg))

More info on lambda can be found here.