Python Dictionaries and Sets

Practice flashcards covering key concepts related to dictionaries and sets in Python.

What is a dictionary in Python?

A collection of key-value pairs with unique keys.

What happens if you try to access a non-existent key in a dictionary?

Raises a KeyError.

How do you add a new key-value pair to a dictionary?

Use dictionary[key] = value.

Which method safely retrieves a value from a dictionary without raising an error if the key doesn’t exist?

dictionary.get(key, default).

What does the popitem() method do?

Removes the last added key-value pair.

Which operator merges two dictionaries into a new one?

| (pipe operator).

What is the output of {1: 'a', 2: 'b'}.values()?

['a', 'b'].

What is a set in Python?

A collection of unique, unordered elements.

How do you add an element to a set?

Use set.add(element).

What is the difference between remove() and discard() for sets?

remove() raises an error if the element doesn’t exist.

Which operator finds the intersection of two sets?

& (ampersand).

What does setA <= setB check?

If setA is a subset of setB.

What is the output of {x**2 for x in {1, 2, 3}}?

{1, 4, 9}.

Which method returns the symmetric difference of two sets?

set1.symmetric_difference(set2).

What does set() with no arguments create?

An empty set.