What's the use of using a lambda function to call a function?

So, as the title suggest, I don't know what's the use of using a lambda function to call another function, especially when putting that lambda function as a keyword argument in a widget such as a button.

def multiply(x,y):
    print(x*y)

window = Tk()

x = 1
y = 1
button = Button(window, text='button' command= lambda x=x, y=y : multiply(x,y))
button.pack()

window.mainloop()

I've been trying to play with it myself. I tried not to use a lambda function to call another function but it's not working as I expected it to be.

What you want is that when you click on your button, your function multiply gets called with the argument "x" and "y"

So achieve this, you need to create a pointer to the function multiply with the right argument, which you can achieve using a lambda expression.

if you were to do button = Button(window, text='button' command= multiply(x,y))

you are not assigning a pointer to a function to the command argument, but instead directly calling multiply(x,y)

you can try this yourself by modify your code

Let's see an example

def print_value(i):
    print(i)


lambda_list = []
normal_list = []

for i in range(0,4):
    normal_list.append(print_value(i))

if you do this, you'll see that 0,1,2,3 gets printed, because I'm calling the function print_value

Now if I do this :

def print_value(i):
    print(i)


lambda_list = []
normal_list = []

for i in range(0,4):
    lambda_list.append(lambda x=i : print_value(x))

Nothing gets printed, because I added pointer to the function inside my list through lambda function, and not directly called the function

but now if I continue my example by doing this

for lambda_func in lambda_list:
    lambda_func()

0,1,2,3 gets printed because I'm now calling my function pointer with the argument I gave to it (through lambda x=i)

now last example

If I were to do

lambda_list = []

for i in range(0,4):
    lambda_list.append(lambda: print_value(i))


for lambda_func in lambda_list:
    lambda_func()

What would be the result? answer : 3 3 3 3

Because when you do lambda x=i : print_value(x) you are capturing the current value of " i " , but when you do lambda: print_value(i), it always references the same "i" (the one of the for loop), ence why you may need to do
lambda x=x, y=y : multiply(x,y) in your case instead of lambda: multiply(x,y)

Hope this is clear.