Set creation in Python - Mini Project: Build & Apply

Set creation

📖 Scenario: You are organizing a small event and want to keep track of unique guests who have RSVP'd. You will use a set to store the names of guests because sets automatically avoid duplicates.

🎯 Goal: Create a set of guest names, add a few names, and then display the set to see the unique guests.

📋 What You'll Learn

Create a set called guests with the names 'Alice', 'Bob', and 'Charlie'.

Create a variable called new_guest and set it to 'Alice'.

Add the new_guest to the guests set.

Print the guests set to show all unique guest names.

💡 Why This Matters

🌍 Real World

Sets are useful to keep track of unique items like guest lists, product IDs, or tags without duplicates.

💼 Career

Understanding sets helps in data cleaning, filtering unique values, and optimizing searches in many programming jobs.

1

Create the initial set of guests

Create a set called guests with these exact names: 'Alice', 'Bob', and 'Charlie'.

Python

# Create the set guests with 'Alice', 'Bob', and 'Charlie'
guests = set()
# Your code here

Hint

Use curly braces {} to create a set with the names inside separated by commas.

2

Add a new guest variable

Create a variable called new_guest and set it to the string 'Alice'.

Python

guests = {'Alice', 'Bob', 'Charlie'}
# Create a variable new_guest and set it to 'Alice'
# Your code here

Hint

Use = to assign the string 'Alice' to the variable new_guest.

3

Add the new guest to the set

Add the guest stored in new_guest to the guests set using the add() method.

Python

guests = {'Alice', 'Bob', 'Charlie'}
new_guest = 'Alice'
# Add new_guest to guests set
# Your code here

Hint

Use guests.add(new_guest) to add the new guest to the set.

4

Display the unique guests

Print the guests set to show all unique guest names.

Python

guests = {'Alice', 'Bob', 'Charlie'}
new_guest = 'Alice'
guests.add(new_guest)
# Print the guests set
# Your code here

Hint

Use print(guests) to display the set. The order may vary but the names should be unique.

Practice

1. Which of the following is the correct way to create a set with the elements 1, 2, and 3 in Python?

easy

A. (1, 2, 3)

B. [1, 2, 3]

C. {1, 2, 3}

D. set[1, 2, 3]

Solution

1. Step 1: Understand set creation syntax

   Sets are created using curly braces with comma-separated values or the set() function.

2. Step 2: Identify correct syntax for set with elements

   {1, 2, 3} correctly creates a set with elements 1, 2, and 3.

3. Final Answer:

   {1, 2, 3} -> Option C

4. Quick Check:

   Curly braces with values = set [OK]

Hint: Use curly braces with commas for sets, not brackets [OK]

Common Mistakes:

• Using square brackets creates a list, not a set
• Using parentheses creates a tuple, not a set
• Using set[] is invalid syntax

2. What is the correct way to create an empty set in Python?

easy

A. set()

B. {}

C. []

D. empty_set()

Solution

1. Step 1: Recognize empty set syntax

   Using {} creates an empty dictionary, not a set.

2. Step 2: Use the set() function for empty sets

   set() correctly creates an empty set.

3. Final Answer:

   set() -> Option A

4. Quick Check:

   Empty set = set() function [OK]

Hint: Empty sets need set(), not curly braces [OK]

Common Mistakes:

• Using {} creates an empty dictionary, not a set
• Using [] creates an empty list
• Using undefined functions like empty_set()

3. What will be the output of the following code?

my_set = {1, 2, 2, 3, 4, 4}
print(my_set)

medium

A. {1, 2, 2, 3, 4, 4}

B. [1, 2, 3, 4]

C. (1, 2, 3, 4)

D. {1, 2, 3, 4}

Solution

1. Step 1: Understand set uniqueness property

   Sets automatically remove duplicate elements, so repeated values appear only once.

2. Step 2: Apply uniqueness to given elements

   Duplicates 2 and 4 are removed, leaving {1, 2, 3, 4}.

3. Final Answer:

   {1, 2, 3, 4} -> Option D

4. Quick Check:

   Sets remove duplicates = {1, 2, 3, 4} [OK]

Hint: Sets keep unique items only, duplicates vanish [OK]

Common Mistakes:

• Expecting duplicates to remain in the set
• Confusing set output with list or tuple syntax
• Thinking sets preserve order

4. Identify the error in the following code snippet:

my_set = set{1, 2, 3}
print(my_set)

medium

A. SyntaxError due to incorrect set creation syntax

B. Prints {1, 2, 3} correctly

C. TypeError because set() expects a list

D. NameError because set is not defined

Solution

1. Step 1: Check set creation syntax

   The correct way to create a set using the function is set() with parentheses, not curly braces.

2. Step 2: Identify syntax error

   set{1, 2, 3} is invalid syntax and causes a SyntaxError.

3. Final Answer:

   SyntaxError due to incorrect set creation syntax -> Option A

4. Quick Check:

   Use set() with parentheses, not braces [OK]

Hint: Use parentheses with set(), not curly braces [OK]

Common Mistakes:

• Using curly braces after set instead of parentheses
• Confusing set() with dictionary syntax
• Assuming set is undefined

5. Given the list nums = [1, 2, 2, 3, 4, 4, 5], which code snippet correctly creates a set of unique elements from this list?

hard

A. unique_nums = {nums}

B. unique_nums = set(nums)

C. unique_nums = list(set(nums))

D. unique_nums = {1, 2, 3, 4, 5}

Solution

1. Step 1: Understand how to convert list to set

   The set() function can take an iterable like a list and return a set of unique elements.

2. Step 2: Analyze each option

   unique_nums = {nums} creates a set with the entire list as one element (invalid). unique_nums = set(nums) correctly converts the list to a set. unique_nums = list(set(nums)) converts to set then back to list, which is not a set. unique_nums = {1, 2, 3, 4, 5} manually writes the set but is not dynamic.

3. Final Answer:

   unique_nums = set(nums) -> Option B

4. Quick Check:

   Use set() on list to get unique elements [OK]

Hint: Use set() on list to get unique items fast [OK]

Common Mistakes:

• Trying to put list inside curly braces directly
• Converting set back to list when set is needed
• Hardcoding values instead of using the list variable