Choice controls: Checkbutton, Radiobutton and Combobox

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Quick Questions

Shade in the A or B circle for each question.

1. Which line creates a variable to store whether a Checkbutton is ticked?

A agree = tk.BooleanVar()

B agree = tk.Checkbutton()

2. A Radiobutton group lets the user pick one size. How do you make the buttons work as one group?

A Give every Radiobutton its own separate variable but the same value=

B Give every Radiobutton the same variable=size but a different value=

3. Which Combobox call correctly supplies the list of options?

A ttk.Combobox(root, options=["Red", "Blue"])

B ttk.Combobox(root, values=["Red", "Blue"])

4. A StringVar called colour is linked to a choice control. How do you read the user's choice?

A colour.get()

B colour.value

5. How do you link a Combobox to a StringVar called pick?

A ttk.Combobox(root, textvariable=pick)

B ttk.Combobox(root, variable=pick)

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Radiobutton(root, text="Small", variable=size, value="S")		Asize = StringVar() Radiobutton(root, text="S", variable=size, value="S") Radiobutton(root, text="L", variable=size, value="L")
2ttk.Combobox(root, textvariable=colour, values=["Red", "Blue"])		BCreates one radio option that sets the shared variable size to "S" when the user selects it
3A Checkbutton stores True or False in a BooleanVar, so you read the tick state with .get()		CNo value= is given, so the buttons have no distinct value to store and cannot be told apart. Add value="S" and value="L".
4A group of Radiobuttons shares ONE variable so that only one option can be selected at a time		Dagree = BooleanVar() Checkbutton(root, text="I agree", variable=agree) print(agree.get())
5Radiobutton(root, text="Small", variable=size) Radiobutton(root, text="Large", variable=size)		EThe variable is printed instead of reading its contents. Use choice.get() to get the user's pick.
6choice = StringVar() print(choice)		FCreates a drop-down list whose chosen item is stored in the variable colour

Definitions

StringVar()

Fill in the Blanks

Complete each line of code by filling in the missing parts.

ok = tk.__________() tk.Checkbutton(win, text="Yes", variable=ok)

tk.Radiobutton(win, variable=size, _____="S")

size = tk.StringVar(value="S") tk.Radiobutton(win, variable=____, value="M")

box = ttk.Combobox(win, ______=["S", "M"])

size = tk.StringVar(value="S") print("Chosen:", size.___())

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A choice = tk.StringVar

B r1 = tk.Radiobutton(win)

C r1.config(text="Yes", value="y")

D r1.config(variable=choice)

Question 2

A agree = tk.BooleanVar()

B cb = tk.Checkbutton(win)

C cb.config(variable="agree")

D print(agree.get())

Question 3

A size = tk.StringVar()

B cb = ttk.Combobox(win)

C cb.config(textvariable=size)

D cb.values = ["S", "M"]

Question 4

A pick = tk.StringVar()

B pick.set("Medium")

C print(pick.value())

Question 5

A pet = tk.StringVar()

B r1 = tk.Radiobutton(win)

C r1.config(textvariable=pet)

D r2 = tk.Radiobutton(win)

E r2.config(variable=pet)

Answer Key

Choice controls: Checkbutton, Radiobutton and Combobox

Section A: Quick Questions

A — agree = tk.BooleanVar()

B — Give every Radiobutton the same variable=size but a different value=

B — ttk.Combobox(root, values=["Red", "Blue"])

A — colour.get()

A — ttk.Combobox(root, textvariable=pick)

Section B: Match the Pairs

Radiobutton(root, text="Small", variable=size, value="S") → Creates one radio option that sets the shared variable size to "S" when the user selects it

ttk.Combobox(root, textvariable=colour, values=["Red", "Blue"]) → Creates a drop-down list whose chosen item is stored in the variable colour

A Checkbutton stores True or False in a BooleanVar, so you read the tick state with .get() → agree = BooleanVar() Checkbutton(root, text="I agree", variable=agree) print(agree.get())

A group of Radiobuttons shares ONE variable so that only one option can be selected at a time → size = StringVar() Radiobutton(root, text="S", variable=size, value="S") Radiobutton(root, text="L", variable=size, value="L")

Radiobutton(root, text="Small", variable=size) Radiobutton(root, text="Large", variable=size) → No value= is given, so the buttons have no distinct value to store and cannot be told apart. Add value="S" and value="L".

choice = StringVar() print(choice) → The variable is printed instead of reading its contents. Use choice.get() to get the user's pick.

Section C: Definitions

StringVar() — A tkinter variable that stores the user's pick from a choice control (Checkbutton, Radiobutton or Combobox). Link it with variable= and read the choice with .get().

Section D: Fill in the Blanks

ok = tk.BooleanVar()
tk.Checkbutton(win, text="Yes", variable=ok)

tk.Radiobutton(win, variable=size, value="S")

size = tk.StringVar(value="S")
tk.Radiobutton(win, variable=size, value="M")

box = ttk.Combobox(win, values=["S", "M"])

size = tk.StringVar(value="S")
print("Chosen:", size.get())

Section E: Spot the Error

A — StringVar is a class, so it must be called with brackets to create the variable object. It should be choice = tk.StringVar().

C — variable= needs the tkinter variable object, not a string with its name. Remove the quotes: cb.config(variable=agree).

D — A Combobox list of options is set with the "values" option, not by creating a Python attribute. It should be cb["values"] = ["S", "M"].

C — A tkinter variable has no .value() method. The user's choice is read with .get(), so it should be print(pick.get()).

C — textvariable sets the text shown on a control. A Radiobutton stores the user's choice using variable=, so it should be r1.config(variable=pet), the same as r2.