Syntax — Python: Dictionaries and Sets

Like other built-in collections, Python supports it and has their syntax for describing literals. Programmers write dictionary literals in curly brackets, separate key-value pairs by commas, and separate the key from the value by colons:

dictionary = {
    "foo": "bar",
    "baz": 42,
    "items": {
        1: "apple",
        2: "orange",
        100500: "lemon"
    },
}
dictionary  # {'foo': 'bar', 'baz': 42, 'items': {1: 'apple', 2: 'orange', 100500: 'lemon'}}

In this example, there are both string and number keys, and one of the values is a nested dictionary. And variables, of course, can act as values and keys:

key, val = 'x', 42
{key: val}  # {'x': 42}

Accessing items by keys

Above, we declared a dictionary called dictionary. You can request a key value from it like this:

dictionary["baz"]  # 42
dictionary["BANG"]  # KeyError: 'BANG'