Dictionary: Use Cases

Dictionaries are extremely versatile and have numerous uses. Here are two major examples:

Dict values: object’s instances

We can have dictionaries where all the values are different instances of objects with the same type. For example, our stock dictionary would have a type hint of dict[str, tuple[float, float, float]]. The string key maps to a three-tuple of values. We use the stock symbol as an index to price details. If we had a more complex Stock class, we might have a dictionary with dict[str, Stock] as the type hint for an index into these objects.

Dict values: object’s attributes

The second design is to have each key represent some aspect or attribute of a single object; the values often have distinct types. We may, for example, represent a stock with {'name': 'GOOG', 'current': 1245.21, 'range': (1252.64, 1245.18)}. This case clearly overlaps with named tuples, data classes, and objects in general. Indeed, a special type hint for this kind of dictionary, called a TypedDict, looks like a NamedTuple type hint.