Frozen set behavior in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an immutable set using the correct function.

Python

my_set = [1]([1, 2, 3])
print(my_set)

Drag options to blanks, or click blank then click option'

Aset

Bfrozenset

Clist

Dtuple

Attempts:

3 left

💡 Hint

Common Mistakes

Using set() instead of frozenset() which creates a mutable set.

Using list() or tuple() which are not sets.

The frozenset() function creates an immutable set in Python.

2fill in blank

medium

Complete the code to check if an element exists in a frozen set.

Python

fset = frozenset([10, 20, 30])
if [1] in fset:
    print("Found")
else:
    print("Not found")

Drag options to blanks, or click blank then click option'

A20

B15

C25

D40

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for a number not in the frozen set, which results in "Not found".

Using a variable name instead of a value.

20 is an element of the frozen set, so the condition is true and "Found" is printed.

3fill in blank

hard

Fix the error in the code by choosing the correct method to add an element to a frozen set.

Python

fset = frozenset([1, 2, 3])
fset = fset.[1]([4])
print(fset)

Drag options to blanks, or click blank then click option'

Aadd

Binsert

Cunion

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use add() or append() which do not work on frozen sets.

Using insert() which is not a set method.

Frozen sets are immutable, so you cannot use add(). Instead, use union() to create a new frozen set with the added element.

4fill in blank

hard

Fill both blanks to create a frozen set from a list and check if it is a subset of another frozen set.

Python

fset1 = frozenset([1])
fset2 = frozenset([1, 2, 3, 4, 5])
print(fset1.[2](fset2))

Drag options to blanks, or click blank then click option'

A[1, 2, 3]

B(1, 2, 3)

Cissubset

Dissuperset

Attempts:

3 left

💡 Hint

Common Mistakes

Using a tuple instead of a list to create the frozen set.

Using issuperset() which checks the opposite relation.

We create fset1 from a list [1, 2, 3] and check if it is a subset of fset2 using issubset().

5fill in blank

hard

Fill all three blanks to create a frozen set, add elements using union, and check the length.

Python

fset = frozenset([1])
fset = fset.[2]([3])
print(len(fset))

Drag options to blanks, or click blank then click option'

A[10, 20]

Bunion

Cfrozenset([30, 40])

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use add which does not work on frozen sets.

Passing a list directly to union instead of a frozen set.

We start with a frozen set of [10, 20], then use union with another frozen set frozenset([30, 40]) to add elements, and finally print the length which is 4.

Practice

1. What is a key characteristic of a frozenset in Python?

easy

A. It is a type of list.

B. It allows duplicate elements.

C. It can be modified by adding or removing elements.

D. It is immutable and cannot be changed after creation.

Solution

1. Step 1: Understand what a frozenset is

   A frozenset is a set that cannot be changed after it is created, meaning it is immutable.

2. Step 2: Compare options with frozenset properties

   'It is immutable and cannot be changed after creation.' correctly states immutability. Claims that it allows duplicate elements or can be modified are false because frozensets do not allow duplicates and cannot be modified. 'It is a type of list.' is incorrect because frozensets are not lists.

3. Final Answer:

   It is immutable and cannot be changed after creation. -> Option D

4. Quick Check:

   Frozen set = immutable set [OK]

Hint: Remember: frozenset means frozen, so no changes allowed [OK]

Common Mistakes:

• Thinking frozensets can be changed like normal sets
• Confusing frozenset with list or tuple
• Assuming duplicates are allowed

2. Which of the following is the correct way to create a frozenset from a list [1, 2, 3]?

easy

A. fs = frozenset([1, 2, 3])

B. fs = frozen_set([1, 2, 3])

C. fs = frozenset{1, 2, 3}

D. fs = frozenset(1, 2, 3)

Solution

1. Step 1: Recall the syntax for creating a frozenset

   The correct syntax uses the function frozenset() with an iterable inside parentheses.

2. Step 2: Evaluate each option

   fs = frozenset([1, 2, 3]) uses frozenset with a list inside parentheses, which is correct. fs = frozen_set([1, 2, 3]) uses a wrong function name. fs = frozenset{1, 2, 3} uses curly braces which is invalid syntax for function calls. fs = frozenset(1, 2, 3) passes multiple arguments instead of one iterable.

3. Final Answer:

   fs = frozenset([1, 2, 3]) -> Option A

4. Quick Check:

   frozenset(iterable) = correct syntax [OK]

Hint: Use frozenset() with one iterable argument inside parentheses [OK]

Common Mistakes:

• Using wrong function name like frozen_set
• Using curly braces instead of parentheses
• Passing multiple arguments instead of one iterable

3. What will be the output of this code?

fs = frozenset([1, 2, 2, 3])
print(len(fs))

medium

A. 4

B. Error

C. 3

D. 2

Solution

1. Step 1: Understand frozenset removes duplicates

   The list has elements [1, 2, 2, 3]. When converted to frozenset, duplicates are removed, so it becomes {1, 2, 3}.

2. Step 2: Calculate length of frozenset

   The frozenset has 3 unique elements, so len(fs) returns 3.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   frozenset removes duplicates, length = 3 [OK]

Hint: Count unique elements only, duplicates are removed [OK]

Common Mistakes:

• Counting duplicates as separate elements
• Expecting an error due to duplicates
• Confusing frozenset with list length

4. What is wrong with this code?

fs = frozenset([1, 2, 3])
fs.add(4)
print(fs)

medium

A. frozenset object has no attribute 'add'

B. It prints {1, 2, 3, 4}

C. It prints {1, 2, 3}

D. SyntaxError

Solution

1. Step 1: Understand frozenset immutability

   frozenset objects cannot be changed after creation, so they do not have methods like add().

2. Step 2: Identify the error when calling add()

   Calling fs.add(4) raises an AttributeError because 'frozenset' has no 'add' method.

3. Final Answer:

   frozenset object has no attribute 'add' -> Option A

4. Quick Check:

   frozenset is immutable, no add() method [OK]

Hint: frozenset has no add or remove methods [OK]

Common Mistakes:

• Trying to add or remove elements from frozenset
• Expecting frozenset to behave like set
• Confusing AttributeError with SyntaxError

5. Given two frozensets:

fs1 = frozenset([1, 2, 3])
fs2 = frozenset([3, 4, 5])

Which expression correctly finds the common elements between fs1 and fs2?

hard

A. fs1 + fs2

B. fs1 & fs2

C. fs1 | fs2

D. fs1 - fs2

Solution

1. Step 1: Recall set operations on frozensets

   frozensets support set operations like intersection (&), union (|), difference (-).

2. Step 2: Identify operation for common elements

   The intersection operator & returns elements common to both sets. So fs1 & fs2 gives {3}.

3. Final Answer:

   fs1 & fs2 -> Option B

4. Quick Check:

   Intersection (&) = common elements [OK]

Hint: Use & operator to find common elements in frozensets [OK]

Common Mistakes:

• Using + which is invalid for sets
• Confusing union (|) with intersection
• Using difference (-) instead of intersection