cooper 0.1.2

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cooper
======

Making super safe, a cooperative methods library

Python's ``super`` is a very useful tool to write cooperative methods.
A **cooperative method** is one such that cooperates with the other
overrides in the same hierarchy. A good example is ``__init__``, as
all the overrides must be called in class-hierarchy ascending order to
properly build an object.

.. image:: doc/gary-cooper.jpg
:align: center

Installation
------------

.. code:: bash

pip install cooper


The problem
-----------

Making cooperative methods in linear hierarchies is simple, but that
is not the case in the presence of multiple inheritance. The problem
lies on the fact that the next override to be called is not known at
class definition time. `James Knight rant
<http://fuhm.net/super-harmful>`_ against ``super`` makes a very clear
exposition of the problem and proposes a methodology to use ``super``
consistently, if used at all.

We believe that ``super`` is very useful and many interesting and
expressive programming patterns arise when using horizontal
hierarchies extensively. This library is attempt to make these safer
and usable in large projects.

Examples
--------

.. code:: python

from cooper import *

Cooperative constructors
````

.. code:: python

class Base(Cooperative):
@cooperate
def __init__(self):
print "Base.__init__"

class Deriv(Base):
@cooperate
def __init__(self):
print "Deriv.__init__"

Deriv()
..

**Output**::

Base.__init__
Deriv.__init__

Automatic argument forwarding
````

.. code:: python

class Base(Cooperative):
@cooperate
def __init__(base_param=None)
print "base_param = ", base_param

class Deriv(Base):
@cooperate
def __init__(deriv_param=None)
print "deriv_param = ", base_param

Base(deriv_param = "Hello",
base_param = "world!")
..

**Output:**::

base_param = Hello
deriv_param = World!


Other methods
````

.. code:: python

class Entity(Cooperative):
@cooperative
def update(self, timer):
print "Entity.update"

class Player(Entity):
@cooperate
def update(self, timer):
print "Player.update"

Player().update(0)
..

**Output:**::

Entity.update
Player.update

Abstract methods
````

.. code:: python

class Abstract(Cooperative):
@abstract
def method(self):
pass

class Concrete(Abstract):
@cooperate
def method(self):
print "Concrete.method"

try:
obj = Abstract()
except TypeError:
print "Abstract could not be instantiated".

obj = Concrete()
obj.method()
..

**Output:**::

Abstract could not be instantiated
Concrete.method

Compatibility with standard abstract methods
````

.. code:: python

import abc

class Abstract(Cooperative):
@abc.abstractmethod
def method(self):
pass

Abstract() # Error
..

Post-cooperation
````

.. code:: python

class Entity(Cooperative):
@cooperative
def dispose(self):
print "Entity.dispose"

class ConcreteEntity(Entity):
@post_cooperate
def dispose(self):
print "ConcreteEntity.dispose"

ConcreteEntity().dispose()
..

**Output:**::

ConcreteEntity.dispose
Entity.dispose

Fix arguments to superclass
````

.. code:: python

class TextWidget(Cooperative):
@cooperate
def __init__(self, color="black", background="white"):
print "color = ", color
print "background = ", background

class ShadedTextWidget(TextWidget):
@cooperate_with_params(color="gray")
def __init__(self):
pass

ShadedTextWidget()
..

**Output:**::

color = gray
background = white

Inner cooperation
````

.. code:: python

import random

class FunnyTextWidget(TextWidget):
@inner_cooperate
def __init__(self, next_method):
random_color = random.choice(["green", "yellow", "red"])
next_method (color = random_color)
..

Manual cooperation
````

.. code:: python

class MockEntity(Entity):
@manual_cooperate
def update(self, timer, **k):
super(MockEntity, self).update(**k)
self.updated_called = True
..

References
----------

- `Python's super is nifty, but you can't use it <http://fuhm.net/super-harmful>`_
- `Python's method resolution order <http://www.python.org/getit/releases/2.3/mro/>`_

License
-------

Copyright (c) 2012, 2015 Juan Pedro Bolivar Puente <raskolnikov@gnu.org>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.