Creating and using dicts

A dictionary holds key–value pairs. You write it with curly braces {}, putting a colon between each key and its value.

Creating a dict

Python

user = {"name": "Alice", "age": 30, "city": "Springfield"}

Each pair is key: value, and pairs are separated by commas. Keys are usually strings, but values can be any type.

Accessing values

Look up a value by putting its key in square brackets:

Python

user = {"name": "Alice", "age": 30}
print(user["name"])   # Alice
print(user["age"])    # 30

If you ask for a key that doesn't exist, Python raises a KeyError.

Adding and updating

Assign to a key to add it (if new) or update it (if it already exists):

Python

user = {"name": "Alice", "age": 30}
user["city"] = "Springfield"   # add a new key
user["age"] = 31               # update an existing key
print(user)
# {'name': 'Alice', 'age': 31, 'city': 'Springfield'}

Key takeaways

Create a dict with {} and key: value pairs.
Read a value with d["key"].
d["key"] = value adds a new key or updates an existing one.