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Building Robust Object-Oriented Python Applications and Libraries

NamedTuple Classes

Understand how to use typing.NamedTuple for immutable data structures and explore the design choice between inheritance and composition. Learn to build composite classes in Python for clean and maintainable code.

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Overview

Using typing.NamedTuple is somewhat similar to using @dataclass(frozen = True). There are some significant differences in the implementation details, however. In particular, the typing.NamedTuple class does not support inheritance in the most obvious way. This leads us to a design based on composition of objects in the Sample class hierarchy. With inheritance, we’re often extending a base class to add features. With composition, we’re often building multi-part objects of several different classes.

Here’s the definition of Sample as NamedTuple. It looks similar to the @dataclass definition. The definition of KnownSample, however, must change dramatically:

Python 3.10.4
class Sample(NamedTuple):
    sepal_length: float
    sepal_width: float
    petal_length: float
    petal_width: float
class KnownSample(NamedTuple):
    sample: Sample
    species: str

The ...