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Immutable struct with sane defaults

Project description

Immutable struct built on top of collections.namedtuple with sane defaults


  • Immutable, dictionary-like data structure
  • Minimal
  • Support required and optional fields (with default values)
  • Strictly disallow positional arguments

Quick Start

First, create an istruct object called person where first_name and last_name are required whereas middle_name, dob and email are optional (with default values specified).

In [1]: from istruct import istruct

In [2]: person = istruct("first_name", "last_name", middle_name="", dob="2000-01-01", email=None)

Then, create an instance of person with first_name, last_name and middle_name.

In [3]: p = person(first_name="Jim", last_name="Raynor", middle_name="Eugene")

In [4]: p
Out[4]: istruct_a3e45e42fb244834bbcbe701210a2931(first_name='Jim', last_name='Raynor', email=None, dob='2000-01-01', middle_name='Eugene')

You can retrieve field values like you would normally do.

In [5]: p.first_name
Out[5]: 'Jim'

In [6]: p.dob
Out[6]: '2000-01-01'

p is immutable, meaning that it cannot be modified after created. Thus, set/delete operations like below would fail, raising an AttributeError.

In [7]: p.first_name = "James"
AttributeError                            Traceback (most recent call last)
<ipython-input-13-681faedb279a> in <module>()
----> 1 p.first_name = "James"

AttributeError: can't set attribute

In [8]: del
AttributeError                            Traceback (most recent call last)
<ipython-input-12-d5c698764d13> in <module>()
----> 1 del

AttributeError: can't delete attribute

istruct only accepts named/keyword arguments. It strictly disallows positional arguments by design.

In [9]: p = person("Jim", "Raynor")
TypeError                                 Traceback (most recent call last)
<ipython-input-14-c0bdbd269e9f> in <module>()
----> 1 p = person("Jim", "Raynor")

TypeError: _istruct() takes 0 positional arguments but 2 were given

However, it would complain when one or more required fields are omitted.

In [10]: p = person(last_name="Raynor")
TypeError                                 Traceback (most recent call last)
<ipython-input-15-451d2add9ee8> in <module>()
----> 1 p = person(last_name="Raynor")

/home/microamp/devel/projs/istruct/ in _istruct(**attrs)
     25     def _istruct(**attrs):
     26         nt = namedtuple(name(), merge_tuples(args, tuple(kwargs.keys())))
---> 27         return nt(**merge_dicts(kwargs, attrs))
     29     return _istruct

TypeError: __new__() missing 1 required positional argument: 'first_name'


  • Find ways to annotate types



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