Set creation in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a set in Python?

A set is a collection of unique items. It does not keep order and does not allow duplicates.

beginner

How do you create an empty set in Python?

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

beginner

Which of these creates a set with elements 1, 2, and 3?

1) {1, 2, 3}
2) set([1, 2, 3])
3) {1, 2, 2, 3}
4) set()

Options 1, 2, and 3 all create a set with elements 1, 2, and 3. Option 3 has a duplicate 2, but sets remove duplicates automatically.

intermediate

Can sets contain mutable items like lists?

No. Sets can only contain immutable (unchangeable) items like numbers, strings, or tuples.

beginner

What happens if you try to create a set with duplicate elements?

Duplicates are automatically removed. The set will only keep one copy of each unique element.

Which syntax creates an empty set in Python?

A {}

B set([])

C []

D set()

Only set() creates an empty set. {} creates an empty dictionary.

What will be the output of {1, 2, 2, 3}?

A {1, 2, 3}

B {1, 2, 2, 3}

C [1, 2, 3]

D (1, 2, 3)

Sets remove duplicates automatically, so only unique elements remain.

Which of these can be an element of a set?

A (1, 2)

B {1: 'a'}

C [1, 2]

D {1, 2}

Tuples are immutable and can be set elements. Lists and dictionaries are mutable and cannot.

What type of collection is a set?

A Unordered and allows duplicates

B Unordered and no duplicates

C Ordered and allows duplicates

D Ordered and no duplicates

Sets are unordered collections that do not allow duplicate elements.

How do you create a set from a list [1, 2, 3]?

A [1, 2, 3].set()

B {[1, 2, 3]}

C set([1, 2, 3])

D set{1, 2, 3}

Use set() with the list as argument to create a set from it.

Explain how to create a set in Python and what makes sets different from lists.

Think about curly braces and the set() function.

Describe what types of elements can be added to a set and why some types are not allowed.

Consider what it means for an object to be unchangeable.