upyls 0.0.4

A collection of python utilities

upyls - A collection of Python utilities

This library can now be found on PyPi or simply installed with:

pip install upyls

Limited List

A List which can have a lower limit nd an upper limit set and only be filled with the number of items set by those limits

Just import and instantiate it

from upyls import LimitedList
limited_list = LimitedList(lower=0, upper=1)

Unit of Work

Implementation of the Unit of Work pattern out of Martin Fowler's book Patterns of Enterprise Application Architecture

UnitOfWorkMixin

This class is an abstract class (derived from ABC). It is designed as mixin, so you just can derive your class from it and your class gets the functionality of this mixin class.

For example:

from upyls import UnitOfWorkMixin

class MyUnitOfWork(UnitOfWorkMixin):
    <your code here>

The added functionality is to keep track of the attributes of the classes instances. If an attribute gets changed, it is marked as dirty and its old value is kept aside the new value.

If you have saved your instance you can call its commit-method and is will not be marked as dirty anymore and its old. value will be discarded. As in database transactions you can as well rollback, which means that the old value is put back into place and the new Value discarded. As well as with committing, the rollback-method leads to the instance not being marked as dirty anymore.

Managing Unit of Works

If you're planning to have multiple objects which you want to be Units of Work it might come handy to be able to manage them all. So if you're using a persistent storage, like a database or simply on disk, you might not want to save every single one on its own, but save them in bulks. After you saved them you should mark all saved ones. For this purpose there's is a derivative of the Unit of Work mixin, which is manageable and a manager class, which exposes the possibility to commit or rollback all manageable Units of Work, that have been registered with the manager. The two classes are very tightly coupled so the methods about connecting a unit with a manager are always two-ways: If you add a manager to a unit the unit will be registered with the manager as well and if it changes it will notify the manager. If you unregister a unit from a manager it also will stop using this manager to notify.

ManageableUnitOfWorkMixin

This class is a derivative of UnitOfWorkMixin and adds the functionality to be manageable by the UnitOfWorkManager. First thi functionality has been in the UnitOfWorkMixin but it added some clutter if you did not want to use it in a manageable way. So it became a derivate, which just contains the extra functionatlity and uses the Unit of Work functionality of its parent.

UnitOfWorkManager

This class offers the functionality to manage a collection of (manageable) Units of Work. It will keep track of registered units that have changed and you can commit all changed units or roll them all back. Of cource you can ask the manager if a certain unit is registered or if it is dirty.

MultiIniParser

The INI-File-Format is around for quite some time and in times of XML and JSON some people might find this format quite archaic, but it is still used in many software projects. There is no real standard for this format, it is rather a set of common practices that define the format. Mostly an INI-File has got a set of sections whcih have Options with values associated with them:

[section]
option=value

Python has got a very good and rich implementation of a parser with configparser.ConfigParser but it does not have support for INI-Files that can have multiple sections or options with the same name or a contain a top level section without a name. While the second case can be worked around the first can not in a simple way. This might be a pretty rare usecase, because in most implementations section and option names have to be unique. But as uncle Murphy turned round the corner, the author stumbled over a service that communicates with a variant of INI-files, which has got an empty top level section AND multiple sections with the same name as well as options with the same name. After having a look at configparser.ConfigParser and how to best subclass it, the author decided to take the ideas and some of the code and turn them to an own class, while it is not impropable that it somewhen will become a subclass of configparser.ConfigParser. It is not meant to steal but meant to extend the functionality in a way that keeps the ideas and interfaces. But in some things it behaves a bit different due to the fact of multiple items. So it often returns Iterables where more than one item can occurr.

This is still work in Progress and it does not yet implement all the possibilities of configparser.ConfigParser but basically it is working.