Tkinter assign button command in a for loop with lambda
Question:
I’m trying to create a few Button
s (with a for
loop) like so:
def a(self, name):
print(name)
users = {"Test": "127.0.0.0", "Test2": "128.0.0.0"}
row = 1
for name in users:
user_button = Tkinter.Button(self.root, text=name,
command=lambda: self.a(name))
user_button.grid(row=row, column=0)
row += 1
and for the buttons to each get their own parameter (Test getting "Test"
and Test2 getting "Test2"
), but when I press the buttons they both print "Test2"
which means they are using the same function with the same parameter.
How can I solve this?
Answers:
The problem is your lambda
expression in the for
loop. It is using the name
variable, but the name
variable gets reassigned each iteration of the for
loop, so in the end, all of the buttons get the last value that name
was assigned to in the for loop. To avoid this you can use default keyword parameters in your lambda
expression like so:
user_button = Tkinter.Button(self.root, text=name,
command=lambda name=name: self.a(name))
This binds the current value of the name
variable to the lambda’s name
keyword argument each time through the loop, producing the desired effect.
I’m trying to create a few Button
s (with a for
loop) like so:
def a(self, name):
print(name)
users = {"Test": "127.0.0.0", "Test2": "128.0.0.0"}
row = 1
for name in users:
user_button = Tkinter.Button(self.root, text=name,
command=lambda: self.a(name))
user_button.grid(row=row, column=0)
row += 1
and for the buttons to each get their own parameter (Test getting "Test"
and Test2 getting "Test2"
), but when I press the buttons they both print "Test2"
which means they are using the same function with the same parameter.
How can I solve this?
The problem is your lambda
expression in the for
loop. It is using the name
variable, but the name
variable gets reassigned each iteration of the for
loop, so in the end, all of the buttons get the last value that name
was assigned to in the for loop. To avoid this you can use default keyword parameters in your lambda
expression like so:
user_button = Tkinter.Button(self.root, text=name,
command=lambda name=name: self.a(name))
This binds the current value of the name
variable to the lambda’s name
keyword argument each time through the loop, producing the desired effect.