Dynamically Adding Tkinter Widgets

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class CheckOut(tk.Frame): #check out page
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        #create and place base widgets
        backGroundPicture = ImageTk.PhotoImage(Image.open("Background.jpg"))
        backGroundLabel = tk.Label(self, image=backGroundPicture, borderwidth=0)
        backGroundLabel.image = backGroundPicture
        backGroundLabel.place(x=0, y=0, anchor=tk.NW)

        checkOutLabel = tk.Label(self, text="Check Out", font=("Verdana", 48), bg="#001f33", fg="red")
        checkOutLabel.place(relx=0.5, rely=0, anchor=tk.N)

        returnButton = tk.Button(self, text="Return to Main Menu", bg="#4db8ff", fg="black",
                           command=lambda: controller.show_frame(StartPage))
        returnButton.place(relx=1, rely=1, anchor=tk.SE)

    ...

Methods of a class in Python pass the object as the first parameter to the method. As a convention, this parameter is named self, but really, you can give it any name.* So add self as a parameter to your update method. I suppose you also wanted to pass a the movie titles as a parameter to the update method.

    ...

    def update(self, movieTitles): #add new widgets displaying items purchase
        print("debug")
        itemLists = []
        for each in movieTitles:
            i = movieTitles.index(each)
            if(adultTickets[i] != 0):
                tempLabel = tk.Label(self, text="Adult Ticket: " + str(adultTickets[i]) + " " + each)
                itemLists.append(tempLabel)
            if(childTickets[i] != 0):
                tempLabel = tk.Label(self, text="Child Ticket: " + str(childTickets[i]) + " " + each)
                itemLists.append(tempLabel)
        for i in itemLists:
            i.place(x=100, y=200, anchor=tk.CENTER)
        print(itemLists)

This way, after having instantiated your object, you can apply its methods like this:

# instantiate object
my_frame = CheckOut(parent, controller)

# apply "update"
my_frame.update(my_movie_titles)

# The previous line has the same effect as this:
CheckOut.update(my_frame, my_movie_titles)

Note: I did not test the code, I just fixed the little syntax mistakes you had in there. At a glance, it seems like the labels for the movies will all have the same position.

Also, as user "zondo" suggests, lambdas here and there clutter the code; getting rid of them can make the code easier to read. A simple occurrence like this can be replaced with the function partial from the functools module:

from functools import partial

returnButton = tk.Button(self, ..., 
    command=partial(controller.show_frame, StartPage))

• Other languages such as C++/Java and family will reserve a keyword instead. (this)