Ada 记录/C++ 结构类型的 Python 对应物是什么? [英] What is the Python counterpart to an Ada record / C++ struct type?

问题描述

假设我正在记录数据并且想要关联一些数据元素，这样每个记录集总是有一个固定的组成，即没有丢失的字段.

Suppose I am recording data and want to associate some number of data elements, such that each recorded set always has a fixed composition, i.e. no missing fields.

我作为程序员的大部分经验都与 Ada 或 C/C++ 变体有关.在 Ada 中，我将使用记录类型和聚合赋值，这样当记录类型更新为新字段时，编译器会通知任何使用该记录的人.在 C++ 中，我可能会使用存储类和构造函数来做类似的事情.

Most of my experience as a programmer is with Ada or C/C++ variants. In Ada, I would use a record type and aggregate assignment, so that when the record type was updated with new fields, anyone using the record would be notified by the compiler. In C++, chances are I would use a storage class and constructor to do something similar.

在 Python 中处理类似情况的合适方法是什么?这是类是正确答案的情况，还是与 Ada 记录类似的重量更轻?

What is the appropriate way to handle a similar situation in Python? Is this a case where classes are the proper answer, or is there a lighter weight analog to the Ada record?

另外一个想法，Ada 记录和 C++ 构造函数都允许默认初始化值.是否有针对上述问题的 Python 解决方案也提供了该功能?

An additional thought, both Ada records and C++ constructors allow for default initialization values. Is there a Python solution to the above question which provides that capability as well?

推荐答案

A namedtuple(来自集合库)可能适合您的目的.它基本上是一个元组，允许按名称和索引位置引用字段.所以它是有序命名字段的固定结构.它也是轻量级的，因为它使用 slots 来定义字段名称，从而消除了在每个实例中都携带字典的需要.

A namedtuple (from the collections library) may suit your purposes. It is basically a tuple which allows reference to fields by name as well as index position. So it's a fixed structure of ordered named fields. It's also lightweight in that it uses slots to define field names thus eliminating the need to carry a dictionary in every instance.

一个典型的用例是定义一个点:

A typical use case is to define a point:

from collections import namedtuple
Point = namedtuple("Point", "x y")
p1 = Point(x=11, y=22)

它的主要缺点是，作为一个元组，它是不可变的.但是有一种方法 replace 允许您用新值替换一个或多个字段，但在此过程中会创建一个新实例.

It's main drawback is that, being a tuple, it is immutable. But there is a method, replace which allows you to replace one or more fields with new values, but a new instance is created in the process.

ActiveState Python Recipes 576555 中还有一个名为 records 的可变版本的命名元组允许直接字段更改.我已经使用过它并且可以保证它运行良好.

There is also a mutable version of namedtuple available at ActiveState Python Recipes 576555 called records which permits direct field changes. I've used it and can vouch that it works well.

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