Dictionaries and Sets

Dictionaries & Sets — cheat sheet

Fast key-value mapping and mathematical set operations in Python.

Dictionary basics

d = {"name": "Alice", "age": 25}

Define key-value pairs.

d["email"] = "a@b.com"

Insert new or update existing key.

val = d.get("role", "guest")

Safe lookup with default fallback.

s = {1, 2, 3}

Set of unique items.

union = s1 | s2

Combine items from both sets.

common = s1 & s2

Intersection: items present in both.