Passing multiple functions as arguments in a lambda function not working

Question

these two functions are not working as args in the lamba function which is calculating the price of the sweets
def mysweets():
    b = v.get( ) # get the value of v set
    cost=int(mysweets_price_list[b]) #price_display
    print(cost)



def quantity_sweets():
    q = int(spinbox1.get())
    print(q)

price = lambda b, q : b * q # final price to be displayed in myLabel_3

print(price(b, q))
I have tried nested functions but they are not working, help please anyone

from tkinter import *

myGui = Tk()
myGui.geometry('450x450+200+200')
myGui.title('Auto Sweet Dispenser')

price_display = ""
b = 0
#a = 0
q = 0
mysweets_price_list = {1 :9.00,
                      2 :7.50,
                      } # dict for the sweet prices

def mysweets():
    b = v.get( ) # get the value of v set
    cost=int(mysweets_price_list[b]) #price_display
    print(cost)



def quantity_sweets():
    q = int(spinbox1.get())
    print(q)

price = lambda b, q : b * q # final price to be displayed in myLabel_3

print(price(b, q))


v =IntVar()
price =IntVar()
v.set(1)

myLabel = Label(myGui,text = 'Choose your sweets',font = 14, fg ='brown').place(x=140,y=55)#grid(row=3,column=10,sticky = 'e')

myRadio_1 = Radiobutton(myGui,text = 'Mints',variable = v, value = 1, command = mysweets).place(x= 160, y = 100)
myRadio_2 = Radiobutton(myGui,text = 'Nut log',variable = v, value = 2, command = mysweets).place(x= 160, y = 120)


myLabel_2 = Label(myGui,text = 'Select Quantity',font = 12, fg ='brown').place(x=160,y=160)#grid(row=3,column=10,sticky = 'e')

myLabel_3 = Label(myGui,textvariable = price ,font = "Times 14 bold",width = 14, fg ='white', bg= 'blue' ,relief = RAISED).place(x=160,y=220)#grid(row=3,column=10,sticky = 'e')


spinbox1 = Spinbox(myGui,from_=1,to = 6,command = quantity_sweets, state = NORMAL)
spinbox1.place(x=160,y=180)#



myGui.mainloop()

the code works except that price is not being displayed as the lambda function is not working.

price is redefined as IntVar() and is no longer a lambda. And price is never updated in your code. — acw1668
– acw1668, Commented Jun 13, 2019 at 0:42

Novel · Accepted Answer · 2019-06-12 16:25:54Z

You don't need lambda here (in general lambda should be extremely rare). You only need a single function to get all the data, do the calculation, and update the Label. Like this:

from tkinter import *

myGui = Tk()
myGui.geometry('450x450+200+200')
myGui.title('Auto Sweet Dispenser')

mysweets_price_list = {1 :9.00,
                      2 :7.50,
                      } # dict for the sweet prices

def calculate():
    b = v.get( ) # get the value of v set
    cost=mysweets_price_list[b] #price

    q = int(spinbox1.get()) # get quantity.

    final_price = cost * q # final price to be displayed
    price.set(final_price)

v =IntVar(value=1) # set initial value to 1
price = IntVar()

Label(myGui,text = 'Choose your sweets',font = 14, fg ='brown').place(x=140,y=55)#grid(row=3,column=10,sticky = 'e')

Radiobutton(myGui,text = 'Mints',variable = v, value = 1, command = calculate).place(x= 160, y = 100)
Radiobutton(myGui,text = 'Nut log',variable = v, value = 2, command = calculate).place(x= 160, y = 120)

Label(myGui,text = 'Select Quantity',font = 12, fg ='brown').place(x=160,y=160)#grid(row=3,column=10,sticky = 'e')

Label(myGui,textvariable = price ,font = "Times 14 bold",width = 14, fg ='white', bg= 'blue' ,relief = RAISED).place(x=160,y=220)#grid(row=3,column=10,sticky = 'e')

spinbox1 = Spinbox(myGui,from_=1,to = 6,command = calculate, state = NORMAL)
spinbox1.place(x=160,y=180)

calculate() # do the calculation at boot
myGui.mainloop()

Also, it's very important to know that if you do name = Widget().place() then the name is set to None and is useless. You need to do

name = Widget()
name.grid() # or pack() or place()

or

Widget().grid() # or pack() or place()

Don't mix those 2 styles! The 2-line style is much better, and what we usually use.

Thank you very much, lots to learn as i'm just a newbiew, my small app is now working.

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