indexed-class 1.0.1

A mechanism for subclass tree indexation.

INDEXED CLASS

Maintainer: aachn3 [e-mail]

Site: https://gitlab.com/pyutil/indexed_class

Version: 1.0.1

About

This package provides some metaclasses/class hierarchy roots capable of storing and retrieving subclasses using arbitrary keys and registry types.

Table of Contents

• structure
• usage
  • examples
• support
  • requirements
  • installation
• tests
  • unit
  • integration

Project Structure

-NoRootClassError(TypeError)
-NoMatchingSubclassError(KeyError)
-SubclassValidationError(ValueError)
-IndexedClassMeta(type)
 -keys
 -operator[]
-IndexedClass(meta=IndexedClassMeta)
-AbstractIndexedClassMeta(IndexedClassMeta, ABCMeta)
-AbstractIndexedClass(meta=AbstractIndexedClassMeta)

Usage

(Abstract)IndexedClassMeta exposes following parameters:

• key (optional, any type): the key under which the class is to be stored in the registry; if the __registry__ attribute is not defined anywhere in parent hierarchy, a NoRootClassError is raised
• root (optional, boolean): if set to True, the class defines a __registry__ attribute as a new instance of the ``@registry_class parameter
• registry_class (optional, type exposing __getitem__, __delitem__ and __setitem__): class used to initialise empty __registry__ in root classes

Methods exposed by classes derived from (Abstract)IndexedClassMeta:

• keys (property): returns a set of all keys defined in __registry__; if this attribute is not defined anywhere in parent hierarchy, a NoRootClassError is raised; by default uses .__registry__.keys() - override if your registry_class does not implement keys() method
• __getitem__(key): returns a class stored in __registry__ under @key; if the __registry__ attribute is not defined anywhere in parent hierarchy, a NoRootClassError is raised; if @key is not found in __registry__, a NoMatchingSubclassError is raised
• __setitem__(key, value): stores @value under @key in __registry__; if the __registry__ attribute is not defined anywhere in parent hierarchy, a NoRootClassError is raised; if @value is not a valid subclass of calling class, a SubclassValidationError is raised
• __delitem__(key): deletes @key from __registry__; if the __registry__ attribute is not defined anywhere in parent hierarchy, a NoRootClassError is raised; if @key is not found in __registry__, a NoMatchingSubclassError is raised

Code samples

Basic usecase

from indexed_class import AbstractIndexedClass, NoMatchingSubclassError
from abc import abstractmethod

import json
import pickle

class FileParser(AbstractIndexedClass, root=True):
    def __init__(self, filename: str):
        self.filename = filename

    @abstractmethod
    def fetch_content(self)->dict:
        raise NotImplementedError("abstract method requires override")

class JsonFileParser(FileParser, key="json"):
    def fetch_content(self)->dict:
        with open(self.filename, "r") as content:
            return json.load(content)

class PickleFileParser(FileParser, key="pickle"):
    def fetch_content(self)->dict:
        with open(self.filename, "rb") as content:
            return pickle.load(content)

### MAIN ###

# example settings:
#   filename: /some/path/data.json
#   filetype: json
with open("settings.json", "r") as file:
    settings = json.load(file)

try:
    data = FileParser[settings["filetype"]](settings["filename"]).fetch_content()
except NoMatchingSubclassError:
    data = None
...

Support

Prerequisites

• python >= 3.8.0

Installation

pip3 install

Testing package functionality

Unit tests

Format: pytest

Integration tests

Format: None