7.3 Using frozen dataclasses to collect data

The third technique for collecting data into a complex structure is the frozen @dataclass. The idea is to create a class that is an immutable collection of named attributes.

Following the example from the previous section, we can have nested dataclasses such as the following:

from dataclasses import dataclass 
 
@dataclass(frozen=True) 
class PointDC: 
    latitude: float 
    longitude: float 
 
@dataclass(frozen=True) 
class LegDC: 
    start: PointDC 
    end: PointDC 
    distance: float

We’ve used a decorator, @dataclass(frozen=True), in front of the class definition to create an immutable (known as ”frozen”) dataclass. The decorator will add a number of functions for us, building a fairly sophisticated class definition without our having to provide anything other...