Immutable struct with sane defaults
Project description
Immutable struct built on top of collections.namedtuple with sane defaults
Goals
Immutable, dictionary-like data structure (Note: istruct is not an immutable version of the existing struct in Python)
Minimal
Support required and optional fields (with default values)
Strictly disallow positional arguments
Installation
pip install istruct
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 p.email
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-12-d5c698764d13> in <module>()
----> 1 del p.email
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/istruct.py in _istruct(**attrs)
25 def _istruct(**attrs):
26 nt = namedtuple(name(), merge_tuples(args, tuple(kwargs.keys())))
---> 27 return nt(**merge_dicts(kwargs, attrs))
28
29 return _istruct
TypeError: __new__() missing 1 required positional argument: 'first_name'
Versions Tested
Python 2.7
Python 3.2
Python 3.3
Python 3.4
PyPy
PyPy3
TODO
Find ways to annotate types
License
MIT