Refactoring code to improve it

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Quick Questions

Shade in the A or B circle for each question.

1. Which best describes refactoring?

A Adding new features to a program so it does more things

B Rewriting working code to be clearer or simpler without changing what it does

2. After refactoring a program, what should you do next?

A Assume it works because you only changed the layout

B Re-run your test cases to check it still gives the same results

3. Which change is an example of refactoring?

A Renaming x to totalPrice so the variable's purpose is clear

B Changing the program so it now also calculates GST

4. A program has the same three lines copied in five places. What is the best refactoring?

A Move the repeated lines into one function and call it where needed

B Copy and paste the lines again so each place is self-contained

5. You rename a variable from n to numStudents. What should the program's output be afterwards?

A Exactly the same as before

B Slightly different because the name is longer

Match the Pairs

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

Left column		Right column
1def calc(a, b): -> def calc_area(width, height):		AThe tests were not re-run, so there is no proof the refactored code still works. Always re-test after refactoring.
2def show_total(price): print("Total: $", price)		Bx = w * h -> area = width * height
3After refactoring, re-run the same test cases to check the program still gives the same results		Cassert calc_area(3, 4) == 12
4Refactoring changes how the code is written but not what it does		DRenaming a function and its variables so the names show their purpose, without changing the result
5area = width * height -> area = width + height		EThe calculation was changed, so the program now behaves differently. That is not refactoring because refactoring must keep the same behaviour.
6Refactor the code, then hand it in without running the tests		FA repeated print line moved into one function that can be called many times

Definitions

refactoring

Fill in the Blanks

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

__________ = price * qty print(totalPrice)

___ showTotal(price, qty): return price * qty

def _________(price, qty): return price * qty print(showTotal(4, 3))

def showTotal(price, qty): return price * qty assert showTotal(2, 3) == _

before = 12 after = showTotal(4, 3) print(before == _____)

Spot the Error

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

Question 1

A def total_price(price, qty):

B return price + qty

C print(total_price(4, 3))

D # expected output: 12

Question 2

A width = 5

B height = 3

C area = width * height

D print(areas)

Question 3

A def greet(name):

B msg = 'Hi ' + name

C print(mesg)

D greet('Sam')

Question 4

A def show_total(cost):

B gst = cost * 0.1

C print(cost + gst

D show_total(20)

E show_total(35)

Question 5

A def average(a, b)

B total = a + b

C return total / 2

D print(average(6, 10))

Answer Key

Refactoring code to improve it

Section A: Quick Questions

B — Rewriting working code to be clearer or simpler without changing what it does

B — Re-run your test cases to check it still gives the same results

A — Renaming x to totalPrice so the variable's purpose is clear

A — Move the repeated lines into one function and call it where needed

A — Exactly the same as before

Section B: Match the Pairs

def calc(a, b): -> def calc_area(width, height): → Renaming a function and its variables so the names show their purpose, without changing the result

def show_total(price): print("Total: $", price) → A repeated print line moved into one function that can be called many times

After refactoring, re-run the same test cases to check the program still gives the same results → assert calc_area(3, 4) == 12

Refactoring changes how the code is written but not what it does → x = w * h -> area = width * height

area = width * height -> area = width + height → The calculation was changed, so the program now behaves differently. That is not refactoring because refactoring must keep the same behaviour.

Refactor the code, then hand it in without running the tests → The tests were not re-run, so there is no proof the refactored code still works. Always re-test after refactoring.

Section C: Definitions

refactoring — Rewriting working code to make it clearer or simpler (e.g. renaming variables, moving repeated lines into a function) without changing what it does, then re-running tests.

Section D: Fill in the Blanks

totalPrice = price * qty
print(totalPrice)

def showTotal(price, qty):
    return price * qty

def showTotal(price, qty):
    return price * qty
print(showTotal(4, 3))

def showTotal(price, qty):
    return price * qty
assert showTotal(2, 3) == 6

before = 12
after = showTotal(4, 3)
print(before == after)

Section E: Spot the Error

B — Refactoring must not change what the code does. Changing * to + gives 7 instead of 12, so the tests would fail. It should be price * qty.

D — The variable was renamed to area, but this line still uses the old name areas, which causes a NameError. It should be print(area).

C — After renaming a variable you must change every use of it. The variable is msg, not mesg. It should be print(msg).

C — The closing bracket is missing, which is a syntax error, so the new function will not run. It should be print(cost + gst).

A — A function definition must end with a colon. Without it the refactored code will not run. It should be def average(a, b):