← ACARA Digital Technologies Years 9–10

Passing a list into a function

A function header with a list parameter. Pass a list when you call it, like total_of([5, 8, 9]), and the function can loop over or read its items.

Part of: ACARA Digital Technologies Years 9–10 — Modular and Object-Oriented Programming (Python) — Module 25, WA Computer Science ATAR Year 11 — Modular Programming — Module 22

Understanding Passing a list into a function in ACARA Digital Technologies Years 9–10

What it does: Because scores is a list parameter, a for loop can visit each item and add it to the running total. Each call passes a different list, so the function works on that list's items each time. Lists are indexed with square brackets. Round brackets would try to call scores like a function. The name in the brackets of the def line is the parameter, and it will hold whatever list the caller passes in.

Common mistakes: A function header must end with a colon. It should be def total_of(scores): so that the indented body belongs to the function. You can't divide a number by a whole list, which causes a TypeError. Divide by the count of items, so it should be return total / count.

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This module's key terms are also in a printable crossword (Modules 629–680) and word search (Modules 629–707).

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Learning

Duo

Which function header takes a list called scores as a parameter?

def total_of[scores]:def total_of(scores):

Matches

def total_of([5, 8, 9]):

↓

A list value was put in the def line. The header needs a parameter name like scores, and the list is passed when calling the function.

Applying

Meanings

Term

def total_of(scores):

Meaning

A function header with a list parameter. Pass a list when you call it, like total_of([5, 8, 9]), and the function can loop over or read its items.

Practice

def total_of(scores):

Testing

Gaps

def total():

Check Answer

Spots

1def total_of(scores)

2 total = 0

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Quick Questions

1. Which function header takes a list called scores as a parameter?

A. def total_of[scores]:

B. def total_of(scores): ✓

A function header uses round brackets around its parameter names. The parameter scores then holds whatever list is passed in.

2. Which call correctly passes a list into total_of()?

A. total_of([5, 8, 9]) ✓

B. total_of(5, 8, 9)

Square brackets build one list, and that single list is passed as one argument. total_of(5, 8, 9) gives three arguments, but the function expects one.

3. Inside def total_of(scores):, what does scores hold when we call total_of([4, 6])?

A. Only the number 4

B. The list [4, 6] ✓

The parameter receives the whole list. You can then loop over it or read items with scores[0], scores[1] and so on.

4. Which loop lets a function read every item in its list parameter scores?

A. for score in scores: ✓

B. for score in total_of:

Loop over the parameter name, scores. total_of is the function's name, not the list.

5. Which statement about calling total_of() is true?

A. You can call it with different lists, such as [5, 8] and [10, 20, 30] ✓

B. It only works with the first list it was ever called with

A parameter is a placeholder. Each call can pass a different list, and the function works on whichever list it receives.

Match the Pairs

def total_of(scores): → Defines a function with a parameter called scores that will receive a list

total_of([5, 8, 9]) → Calls the function and passes in a list of three numbers

The function can loop over every item in the list it was given → for s in scores: total += s

The same function can be reused with different lists → total_of(maths) total_of(science)

def total_of([5, 8, 9]): → A list value was put in the def line. The header needs a parameter name like scores, and the list is passed when calling the function.

total_of(scores) # scores was never created → The call uses a list variable that has not been created, so Python raises a NameError.

Key Term

def total_of(scores):

A function header with a list parameter. Pass a list when you call it, like total_of([5, 8, 9]), and the function can loop over or read its items.

Fill in the Blanks

1. def total(scores): result = 0 for s in scores:

Hint: Type the parameter name that will hold the list passed in. The loop below uses it.

2. def total(scores): return sum(scores)

Hint: Type the built-in function that adds up all the items in the list parameter.

3. def total(scores): result = 0 for score in scores:

Hint: Type the keyword that makes the loop go through each item of the list parameter.

4. marks = [70, 85, 90] print(total(marks))

Hint: Type the name of the variable holding the list so it is passed to the function as an argument.

5. def average(scores): return sum(scores) / len(scores)

Hint: Type the built-in function that counts how many items are in the list parameter.

Spot the Error

Question 1

A def total_of(scores)

B total = 0

C for s in scores:

D total += s

E return total

Line A — A function header must end with a colon. It should be def total_of(scores): so that the indented body belongs to the function.

Question 2

A def average(marks):

B total = sum(marks)

C count = len(marks)

D return total / marks

E print(average([70, 80, 90]))

Line D — You can't divide a number by a whole list, which causes a TypeError. Divide by the count of items, so it should be return total / count.

Question 3

A def biggest(nums):

B top = nums[0]

C for n in nums:

D if n > top

E top = n

F return top

Line D — An if statement needs a colon at the end of the line. It should be if n > top: so the indented line below runs when the test is true.

Question 4

A def show_all(names):

B for name in names:

C print(nam)

D show_all(['Ava', 'Liam'])

Line C — The loop variable is called name, not nam. Using nam causes a NameError. It should be print(name).

Question 5

A def count_pass(marks):

B passed = 0

C for m in range(marks):

D if m >= 50:

E passed += 1

F return passed

Line C — range() needs a number, not a list, so this causes a TypeError. To loop over the items in the list parameter, write for m in marks:.

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