Dictionaries

Dictionaries store key/value pairs. Keys must be unique and immutable.

Creating Dictionaries

empty = {}
person = {"name": "Jack", "age": 26}
mixed = {1: "apple", "colors": ["red", "green"]}

from_pairs = dict([(1, "a"), (2, "b")])

Accessing Values

print(person["name"])      # Jack
print(person.get("age"))   # 26
print(person.get("city"))  # None

Adding and Updating

person["age"] = 27
person["city"] = "Downtown"

Removing

scores = {1: 1, 2: 4, 3: 9}
scores.pop(2)     # removes key 2
scores.popitem()  # removes last inserted item (Python 3.7+)
del scores[1]
scores.clear()

Common Methods

person = {"name": "Jack", "age": 26}

print(person.keys())
print(person.values())
print(person.items())

Dictionary Comprehension

squares = {x: x * x for x in range(6)}
odd_squares = {x: x * x for x in range(11) if x % 2 == 1}

Membership and Iteration

print("name" in person)  # True

for key, value in person.items():
    print(key, value)

Previous