tkinter: checkbox doesn't update in for-loop

I'm stuck on the following problem. With a for-loop, I want to make a few checkboxes which automatically update a label stating whether the checkbox is ticked or not. However, it gives the wrong results (it always says that the checkboxes are ticked, whether this is the case or not; noteworthy is the fact that the checkboxes are unticked by default), see here how the GUI looks like (including error). The IntVars corresponding with the checkboxes are working correctly, as can be seen when ticking at least one of the checkboxes and pressing a button whose function is to read the checkboxes. See also the following code:

import tkinter as tk

top = tk.Tk()
n_passes = 3

checkbox_var = [0] * n_passes
checkbox = [0] * n_passes

def tick_passes(i): # update label saying if checkboxes are ticked
    if checkbox_var[i].get == 0:
        label = tk.Label(top, text = f"pass #{i} not ticked")
    else:
        label = tk.Label(top, text = f"pass #{i} ticked")
    label.grid(row = 1, column = i)

def check_checkbox_var(): # check whether checkbox_var[i] is updated
    for i in range(n_passes):
        print(f"checkbox_var[i].get() = {checkbox_var[i].get()}")

for i in range(n_passes):
    checkbox_var[i] = tk.IntVar() # turn on/off certain passes
    print(f"checkbox_var[i].get() = {checkbox_var[i].get()}")
    checkbox[i] = tk.Checkbutton(top, text = f"Tick pass {i}", variable =
    checkbox_var[i], command = tick_passes(i))
    checkbox[i].grid(row = 0, column = i, sticky=tk.W)

    var_button = tk.Button(top, text = "Check checkbox_var", command =
    check_checkbox_var).grid(row = 2, column = 0) # check whether checkbox_var[i] is updated

top.mainloop()

Could somebody help me in updating the labels? If there is another way to fix this issue, e.g. with buttons to be pressed instead of checkbuttons to be ticked, this would also help me a lot. Thanks a lot in advance for your help!