Procedures versus functions

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Quick Questions

Shade in the A or B circle for each question.

1. Which best describes a procedure?

A It carries out a task, such as printing, without returning a value

B It always sends a value back to the code that called it

2. Which best describes a function?

A It returns a value to the code that called it

B It can never be used inside an expression or stored in a variable

3. Which of these is a procedure? def show_welcome(name): print("Welcome,", name)

A show_welcome, because it only prints and has no return

B show_welcome, because it has a parameter

4. Which of these is a function?

A def say_hi(): print("Hi")

B def double(n): return n * 2

5. Which line stores the result of a call in a variable?

A total = show_message("Hi") # show_message only prints

B total = add(3, 4) # add returns a value

Match the Pairs

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

Left column		Right column
1def show_menu(): print("1. Play")		Ashow_menu()
2def add(a, b): return a + b		BA function: it sends a value back to the code that called it so the result can be stored or used
3A function's returned value can be stored in a variable for later use		CA procedure: it carries out a task (printing) but does not return a value to the caller
4A procedure is called as its own statement because it has no result to store		Darea only prints and has no return, so it is a procedure. size stores None, not 12. Use return w * h to make it a function.
5def area(w, h): print(w * h) size = area(3, 4)		Etotal = add(2, 3)
6def greet(name): return "Hi " + name greet("Sam")		Fgreet returns a value but the result is never printed or stored, so nothing is shown. Use print(greet("Sam")) or store it in a variable.

Definitions

procedure vs function

Fill in the Blanks

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

def showTotal(a, b): _____(a + b)

def add(a, b): ______ a + b

def add(a, b): return a + b total = ___(2, 3)

___ showMenu(): print("1. Play") print("2. Quit")

def showArea(w, h): print(w * h) ________(3, 4)

Spot the Error

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

Question 1

A def say_hi(name):

B return "Hi, " + name

C say_hi("Ava")

Question 2

A def area(w, h):

B result = w * h

C return

D print(area(3, 4))

Question 3

A def show_menu():

B print("1. Play")

C print("2. Quit")

D show_menu

Question 4

A def square(n):

B n * n

C answer = square(5)

D print(answer)

Question 5

A def get_double(n)

B return n * 2

C print(get_double(4))

Answer Key

Procedures versus functions

Section A: Quick Questions

A — It carries out a task, such as printing, without returning a value

A — It returns a value to the code that called it

A — show_welcome, because it only prints and has no return

B — def double(n): return n * 2

B — total = add(3, 4) # add returns a value

Section B: Match the Pairs

def show_menu(): print("1. Play") → A procedure: it carries out a task (printing) but does not return a value to the caller

def add(a, b): return a + b → A function: it sends a value back to the code that called it so the result can be stored or used

A function's returned value can be stored in a variable for later use → total = add(2, 3)

A procedure is called as its own statement because it has no result to store → show_menu()

def area(w, h): print(w * h) size = area(3, 4) → area only prints and has no return, so it is a procedure. size stores None, not 12. Use return w * h to make it a function.

def greet(name): return "Hi " + name greet("Sam") → greet returns a value but the result is never printed or stored, so nothing is shown. Use print(greet("Sam")) or store it in a variable.

Section C: Definitions

procedure vs function — A procedure carries out a task without returning a value, while a function returns a value to the code that called it, so the result can be stored or used.

Section D: Fill in the Blanks

def showTotal(a, b):
    print(a + b)

def add(a, b):
    return a + b

def add(a, b):
    return a + b
total = add(2, 3)

def showMenu():
    print("1. Play")
    print("2. Quit")

def showArea(w, h):
    print(w * h)
showArea(3, 4)

Section E: Spot the Error

B — say_hi is a procedure that should print its message. With return, the text goes back to the caller, which does nothing with it, so nothing is shown. It should be print("Hi, " + name).

C — A function must send its answer back to the caller. A bare return gives back None, so print() would show None instead of 12. It should be return result.

D — Without brackets the procedure is only named, not called, so its code never runs and nothing prints. It should be show_menu().

B — The multiplication is worked out but never returned. The function gives back None, so answer would be None. It should be return n * n.

A — A function definition header must end with a colon. It should be def get_double(n):.