free-properties 0.3.6
Manage properties outside a class
License: MIT

===============
free_properties
===============

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.. contents::

What is free_properties?
------------------------

free_properties is a python package that features the FreeProperty class. A FreePropety object behaves just like its value property, allowing it to be used as a proxy for get, and set calculations like a python property.

Installation
------------

Get the latest version of free_properties from
https://pypi.python.org/pypi/free_properties/

If you have an installation of Python with pip, simple install it with:

    $ pip install free_properties

To get the git version, run:

    $ git clone git://github.com/yoelcortes/free_properties

Documentation
-------------

free_properties's documentation is available on the web:

    http://free_properties.readthedocs.io/

Getting started
---------------

The PropertyFactory is a FreeProperty class creator that functions similar to Python 'property' objects. Use the PropertyFactory to create a Weight class which calculates weight based on density and volume:
    
.. code-block:: python
    
    >>> from free_properties import PropertyFactory
    >>> def getter(self):
    ...    '''Weight (kg) based on volume (m^3).'''
    ...    data = self.data
    ...    rho = data['rho'] # Density (kg/m^3)
    ...    vol = data['vol'] # Volume (m^3)
    ...    return rho * vol
    >>>
    >>> def setter(self, weight):
    ...    data = self.data
    ...    rho = data['rho'] # Density (kg/m^3)
    ...    data['vol'] = weight / rho
    >>>
    >>> # Initialize with a value getter, setter, and the class name.
    >>> Weight = PropertyFactory(getter, setter, 'Weight', units='kg')
    
It is more convinient to use the PropertyFactory as a decorator:

.. code-block:: python
   
    >>> @PropertyFactory(units='kg')
    >>> def Weight(self):
    ...    '''Weight (kg) based on volume (m^3).'''
    ...    data = self.data
    ...    rho = data['rho'] # Density (kg/m^3)
    ...    vol = data['vol'] # Volume (m^3)
    ...    return rho * vol
    >>>
    >>> @Weight.setter
    >>> def Weight(self, weight):
    ...    data = self.data
    ...    rho = data['rho'] # Density (kg/m^3)
    ...    data['vol'] = weight / rho
   

Create dictionaries of data and initialize new Weight objects:
   
.. code-block:: python
   
   >>> water_data = {'rho': 1000, 'vol': 3}
   >>> ethanol_data = {'rho': 789, 'vol': 3}
   >>> weight_water = Weight('Water', water_data)
   >>> weight_ethanol = Weight('Ethanol', ethanol_data)
   >>> weight_water
   <Water: 3000 kg>
   >>> weight_ethanol
   <Ethanol: 2367 kg>

These properties behave just like their dynamic value:

.. code-block:: python

    >>> weight_water + 30
    3030
    >>> weight_water + weight_ethanol
    5367
    
Get and set the value through the 'value' attribute:
    
.. code-block:: python

    >>> weight_water.value
    3000
    >>> weight_water.value = 4000 
    >>> weight_water.value
    4000
    >>> water_data # Note that the volume changed too
    {'rho': 1000, 'vol': 4}

In place magic methods will also change the property value:

.. code-block:: python

    >>> weight_water -= 1000
    >>> weight_water
    <Weight(Water): 3000 kg>
    >>> water_data  # The change also affects the original data
    {'rho': 1000, 'vol': 3}
    
Use the property_array to manage free properties as an array:
           
.. code-block:: python
   
   >>> from free_properties import property_array
   >>> prop_arr = property_array([weight_water, weight_ethanol])
   >>> prop_arr
   property_array([3000.0, 2367.0], dtype=object)
   >>> prop_arr.sum()
   5367.0
   
Changing the values of a property_array changes the value of its properties:
   
.. code-block:: python
   
   >>> # Addition in place
   >>> prop_arr += 3000
   >>> prop_arr
   property_array([6000.0, 5367.0], dtype=object)
   >>> # Note how the data also changes
   >>> water_data
   {'rho': 1000, 'vol': 6.0}
   >>> ethanol_data
   {'rho': 789, 'vol': 6.802281368821292}
   >>> # Setting an item changes the property value
   >>> prop_arr[1] = 2367
   >>> ethanol_data
   {'rho': 789, 'vol': 3}
  
New arrays have no connection to the property_array:
   
.. code-block:: python
   
   >>> prop_arr - 1000 #  Returns a new array
   array([5000.0, 1367.0], dtype=object)
   >>> water_data #  Data remains unchanged
   {'rho': 1000, 'vol': 6.0}

Latest source code
------------------

The latest development version of free_properties's sources can be obtained at:

    https://github.com/yoelcortes/free_properties


Bug reports
-----------

To report bugs, please use the free_properties' Bug Tracker at:

    https://github.com/yoelcortes/free_properties

License information
-------------------

See ``LICENSE.txt`` for information on the terms & conditions for usage
of this software, and a DISCLAIMER OF ALL WARRANTIES.

Although not required by the free_properties' license, if it is convenient for you,
please cite free_properties if used in your work. Please also consider contributing
any changes you make back, and benefit the community.


Citation
--------

To cite free_properties in publications use::

    Yoel Cortes-Pena (2019). free_properties: Manage properties outside a class.
    https://github.com/yoelcortes/free_properties