On 12/08/2014 09:30 PM, Ben Finney wrote:
memilanuk <memila...@gmail.com> writes:
...
lambda: update_label2('A', 100)
would this work the same?
(I don't know what you mean here by “the same”; the same as what?)
The above creates a new function, which expects no parameters (because
there are no parameters before its ‘:’).
The function, when called, will return the value of the expression
‘update_label2('A', 100)’.
It looks as though it'd be passing the same two parameters to the same
function...
Yes, it looks that way, and that's what it does. The parameters are
fixed in the expression and will be the same each time the new function
is called.
lambda: 'A', 100: update_label2()
This is a syntax error.
Have you tried experimenting with these? Carefully read the reference
material on the ‘lambda’ syntax, and create some functions and
experiment with them.
Fair enough. What I was trying to do when I got into all this was
something like this:
import tkinter as tk
root = tk.Tk()
root.wm_title('Radio Buttons')
label1 = tk.Label(root)
label1.config(text='Please select an option below.')
label1.pack()
def update_label2(option, value):
selection = "current selection is: \n\n" + str(option) + ": " +
str(value)
label2.config(text=selection)
var = tk.IntVar()
var.set(100)
R1 = tk.Radiobutton(root, text='A', value=100, variable=var,
command=lambda: update_label2('A', 100))
R1.pack(anchor='center')
R2 = tk.Radiobutton(root, text='B', value=80, variable=var,
command=lambda option='B', value=80: update_label2())
R2.pack(anchor='center')
R3 = tk.Radiobutton(root, text='C', value=60, variable=var,
command=lambda: update_label2('C', 60))
R3.pack(anchor='center')
label2 = tk.Label(root)
label2.config(text='Current selection is: \n \nA: 100')
label2.pack()
root.mainloop()
So to me, the purpose of 'lambda' in this case is to call a function
when a particular widget - in this case a radio button - is clicked.
Thats why I wondered if 'lambda: update_label2('A', 100)' - where I'm
using lambda to call another function, with the parameters inside the
parentheses, was equivalent to 'lambda 'A', 100: update_label2()' where
I would be using lambda to 'feed' the parameters to the function. I see
what you mean about the syntax error = it should be 'lambda option='A',
value=100:update_label2()' but even then it doesn't really work as the
update_label2 function complains about not being given any values at all.
File "/home/monte/Dropbox/Code/python/sandbox/reddit.py", line 31, in
<lambda>
command=lambda option='B', value=80: update_label2())
TypeError: update_label2() missing 2 required positional arguments:
'option' and 'value'
--
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Reach me @ memilanuk (at) gmail dot com
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