CSE 160 Section 7

Tuples & Mutability!

CSE 160: Tuples & Mutability

Logistics

• Written check-in 7 due Friday Feb 20!
• Programming practice 7 due Wed, Feb 25!
• HW4 due Thu Feb 26
• Submitting on Gradescope
• Wait for autograder!

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CSE 160: Tuples & Mutability

Lecture Review: Tuples

CSE 160: Tuples & Mutability

Tuples

• Tuple is a collection which is ordered and unchangeable.
• Lists and tuples are similar, but have different properties
• The table at the right shows what kind of things you can do with a tuple, but not a list.
• Let the data structure be called name. A ✅ means you can do it, a 🚫 means it won’t work

CSE 160: Tuples & Mutability

Making a Tuple

These are all ways to make tuples:

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Note that to make a one element tuple you need to add a comma after the one value! (1) would not work!

t = tuple([1, 2, 3])

t = (1, 2, 3)

t = (1,)

CSE 160: Tuples & Mutability

Lecture Review: Mutability

CSE 160: Tuples & Mutability

What is Mutable?

Mutable = Can Change

A mutable object can be changed after it is created.

Example:

my_list = [1, 2, 3]

my_list.append(4)

print(my_list)

Output:

[1, 2, 3, 4]

The list changed directly.

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Common Mutable Types:

• list�
• dictionary (dict)�

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CSE 160: Tuples & Mutability

What is Immutable?

Immutable = Cannot Change

An immutable object cannot be changed after it is created.

Example:

x = 5

x = x + 1

print(x)

Output:

6

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The original 5 was not changed.� Python created a new object 6.

Common Immutable Types:

• int�
• float�
• string (str)�
• tuple�
• bool

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CSE 160: Tuples & Mutability

A tuple is an immutable sequence

• Lists, strings, and tuples are all ordered sequences
• Strings and tuples are immutable
• The elements of a tuple can be anything
• (including mutable types)

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# Creating tuples

w = (4, 7, 9)

x = ("once", "upon", "a", "time")

y = () # An empty tuple

z = "rea2000", "blue" # parenthesis can make things � # clearer but are often not needed

Python Tutor

CSE 160: Tuples & Mutability

Section Handout Problems

CSE 160: Tuples & Mutability

Problem 1

A marathon race has recorded the finishing results of several runners.

Each runner's information is stored in a tuple in the format:

(runner_name, country, finish_time_minutes)

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Your goal is to:

Part A:

1. Print each runner’s name and finish time.

Part B:

2. Determine the fastest runner and their time.

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You must use indexing

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CSE 160: Tuples & Mutability

Problem 2

Write code that does the following, given study_hours which is a dictionary where the key is the subject and the value is the number of hours studied.:

1. Prints each subject and the number of hours studied
2. Labels the subject "Good" if the hours are 4 or more, otherwise "Needs more practice"
3. Calculates the total number of hours studied
4. Counts how many subjects are labeled "Good"

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study_hours = {

"Math": 4,

"English": 3,

"Science": 6,

"History": 2,

"Computer Science": 5

}

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Expected Output:

Math: 4 hours (Good)

English: 3 hours (Needs more practice)

Science: 6 hours (Good)

History: 2 hours (Needs more practice)

Computer Science: 5 hours (Good)

CSE 160: Tuples & Mutability

Problem 3

Write a function called analyze_scores(score_list) that takes in one parameter score_list, which is a list of student scores. The function should do the following:

• Find the highest score (highest_score)
• Find the lowest score (lowest_score)
• Count how many students scored 80 or higher (count_80_or_more)

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The function must return all three values as a tuple in this order:

(highest_score, lowest_score, count_80_or_more)

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Example call to function:

scores = [88, 72, 90, 65, 78, 94, 55, 83, 100, 67, 81]

highest_score, lowest_score, count_80_or_more = analyze_scores(scores)

Expected output:

(100, 55, 6)

CSE 160: Tuples & Mutability

Problem 4A

Problem 4. Part A and Part B refer to the code below.

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list_1 = [0, 5, 10]

list_2 = ['a', 'z']

list_3 = [100]

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print("Before, list_1:", list_1)

print("Before, list_2:", list_2)

print("Before, list_3:", list_3)

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def test_mutability(a, b, c):

a[0] = [3]

b = ['b']

c = [c[0] + 1]

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test_mutability(list_1, list_2, list_3)

print("After, list_1:", list_1)

print("After, list_2:", list_2)

print("After, list_3:", list_3)

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Part A. What does the following code output?

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CSE 160: Tuples & Mutability

Problem 4A

Problem 4. Part A and Part B refer to the code below.

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list_1 = [0, 5, 10]

list_2 = ['a', 'z']

list_3 = [100]

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print("Before, list_1:", list_1)

print("Before, list_2:", list_2)

print("Before, list_3:", list_3)

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def test_mutability(a, b, c):

a[0] = [3]

b = ['b']

c = [c[0] + 1]

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test_mutability(list_1, list_2, list_3)

print("After, list_1:", list_1)

print("After, list_2:", list_2)

print("After, list_3:", list_3)

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Part A. What does the following code output?

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CSE 160: Tuples & Mutability

Problem 4B

Problem 4. Part A and Part B refer to the code below.

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list_1 = [0, 5, 10]

list_2 = ['a', 'z']

list_3 = [100]

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print("Before, list_1:", list_1)

print("Before, list_2:", list_2)

print("Before, list_3:", list_3)

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def test_mutability(a, b, c):

a[0] = [3]

b = ['b']

c = [c[0] + 1]

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test_mutability(list_1, list_2, list_3)

print("After, list_1:", list_1)

print("After, list_2:", list_2)

print("After, list_3:", list_3)

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Part B. What happened? Why is this the output once the test_mutability is called?

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CSE 160: Tuples & Mutability

Problem 4B

Problem 4. Part A and Part B refer to the code below.

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list_1 = [0, 5, 10]

list_2 = ['a', 'z']

list_3 = [100]

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print("Before, list_1:", list_1)

print("Before, list_2:", list_2)

print("Before, list_3:", list_3)

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def test_mutability(a, b, c):

a[0] = [3]

b = ['b']

c = [c[0] + 1]

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test_mutability(list_1, list_2, list_3)

print("After, list_1:", list_1)

print("After, list_2:", list_2)

print("After, list_3:", list_3)

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Part B. What happened? Why is this the output once the test_mutability is called?

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CSE 160: Tuples & Mutability

Written Check-In

CSE 160: Tuples & Mutability