Headline

The Borg Pattern in Language:Python

Motivation

This implementation illustrates the Borg Pattern in Python, it is similar to the singleton pattern but the singleton pattern ensures instance equality which the Borg pattern does not, instead it ensures state equality. Using this pattern, one has several instances but they all have the exact same state. An advantage of this pattern is the possibility to write normal python classes and deriving from the Borg class is sufficient to make it a "Borg".

Illustration

The data model is mostly adapted from Contribution:py3k.

class Borg(object):

      state = {}
    def   init  (self):
        self.  dict   = Borg.  state
        

This class makes sure that all instances of a class derived from the Borg class have the exact same state by writing to the " dict " attribute which holds all attributes and methods of an object in Python. The Company class is very similar to the normal version.

class Company(Borg):
    
    def   init  (self, name, subunits):
        Borg.  init  (self)
        self.name = name
        self.subunits = subunits


By deriving from the Borg class, you can do this:

company = Company(
    "Meganalysis", ["..."])
    
    first total = company.total()
     
    company2 = Company("Meganalysis",["..."])
    
    company2.cut()
    assert company.total() * 2.0 == first total

Usage

Just run python program.py

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    For you are available next options:

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    will allow you to paste code headline into the page.

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    will allow your to insert slideshare presentation into the page. You need to copy link to presentation and insert it as parameter in this tag.

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