Why is the variable always set to the last item in the list?

Question

Using tkinter and python to build a GUI and I'm adding buttons using globals() based off a list of room_types. However, the variable I'm passing into the button's command is always the last item on the list, even though every other instance of using room_type[i] correlates to the correct element.

This is what I'm having problems with.

from tkinter import *

root = Tk()

room_type = ['kitchen', 'living_room', 'bedroom', 'bathroom', 'study', 'laundry', 'dining_room']


def new_room(r):
    print(r)


for i in range(len(room_type)):
    globals()[f'{room_type[i]}_add'] = Button(root, text='Add a ' + room_type[i],
                                              command=lambda: new_room(r=room_type[i]))
    globals()[f'{room_type[i]}_add'].grid(row=1, column=i)

root.mainloop()

It makes 7 buttons, each with text that indicates the different room types, but for some reason, r always equals the last element in the list. In this case, dining_room.

Answer 1

Capture the current value of i when declaring the lambda:

from tkinter import *

root = Tk()

room_type = ['kitchen', 'living_room', 'bedroom', 'bathroom', 'study', 'laundry', 'dining_room']


def new_room(r):
    print(r)


for i in range(len(room_type)):
    globals()[f'{room_type[i]}_add'] = Button(root, text='Add a ' + room_type[i],
                                              command=lambda pi=i: new_room(r=room_type[pi]))
    globals()[f'{room_type[i]}_add'].grid(row=1, column=i)

root.mainloop()