==========================
Python orientado a objetos
==========================

.. testsetup::

    class Circle:
        PI = 3.14

        @classmethod
        def create_small_circle(cls):
            return cls(0.001)

        @staticmethod
        def angle_to_rad(grades):
            return 2 * Circle.PI * grades / 360

        def __init__(self, radius):
            self.radius = radius

        def perimeter(self):
            return 2 * self.PI * self.radius

        def grow(self, inc):
            self.radius = self.radius + inc

    class FilledCircle(Circle):

            def area(self):
                return self.PI * (self.radius ** 2)

    class DoubleFilledCircle(FilledCircle):

        def area(self):
            rv = super().area()
            return 2 * rv

Clases
======

En capítulos anteriores
-----------------------

.. code:: python

    class Circle:
        PI = 3.14

        def __init__(self, radius):
            self.radius = radius

        def perimeter(self):
            return 2 * self.PI * self.radius

.. nextslide::

.. doctest::

        >>> a_circle = Circle(3)
        >>> a_circle.radius
        3
        >>> a_circle.perimeter()
        18.84

.. nextslide::

.. doctest::

        >>> a_circle = Circle(3)
        >>> a_circle.radius
        3
        >>> a_circle.radius = 1
        >>> a_circle.radius
        1
        >>> a_circle.perimeter()
        6.28

Modificar propiedades
---------------------

.. code:: python

    class Circle:
        PI = 3.14

        def __init__(self, radius):
            self.radius = radius

        def perimeter(self):
            return 2 * self.PI * self.radius

        def grow(self, inc):
            self.radius = self.radius + inc


.. nextslide::

.. doctest::

        >>> a_circle = Circle(3)
        >>> a_circle.radius
        3
        >>> a_circle.grow(2)
        >>> a_circle.radius
        5

Herencia
--------

.. code::

    class Nombreclasederivada(Nombreclasebase):
        expresión 1
        expresión 2
        .
        expresión N

.. code:: python

        class FilledCircle(Circle):
            def area(self):
                return self.PI * (self.radius ** 2)

.. doctest::

        >>> a_filled_circle = FilledCircle(3)
        >>> a_filled_circle.radius
        3
        >>> a_filled_circle.perimeter()
        18.84
        >>> a_filled_circle.area()
        28.26

Herencia: invocación ancestro
-----------------------------

.. code:: python

        class DoubleFilledCircle(FilledCircle):
            def area(self):
                rv = super().area()
                return 2 * rv

.. doctest::

        >>> a_double_filled_circle = DoubleFilledCircle(3)
        >>> a_double_filled_circle.radius
        3
        >>> a_double_filled_circle.perimeter()
        18.84
        >>> a_double_filled_circle.area()
        56.52

Herencia múltiple
-----------------

.. code::

    class Nombreclasederivada(Nombreclasebase1, Nombreclasebase2, ...):
        expresión 1
        expresión 2
        .
        expresión N

Propiedades solo lectura
------------------------

.. code:: python

    class Feline:
        def __init__(self, name):
            self._name = name

        @property
        def name(self):
            return self._name.capitalize()

.. testsetup:: *

    class Feline:
        def __init__(self, name):
            self._name = name

        @property
        def name(self):
            return self._name.capitalize()

.. doctest::

    >>> cat = Feline('garfield')
    >>> cat.name
    'Garfield'
    >>> cat.name = 'Pluto'
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
        cat.name = 'Pluto'
    AttributeError: can't set attribute

Propiedades lectura/escritura
-----------------------------

.. code:: python

    class Feline2:
        def __init__(self, name):
            self._name = name

        @property
        def name(self):
            return self._name.capitalize()

        @name.setter
        def name(self, value):
            self._name = value

.. testsetup:: *

    class Feline2:
        def __init__(self, name):
            self._name = name

        @property
        def name(self):
            return self._name.capitalize()

        @name.setter
        def name(self, value):
            self._name = value

.. doctest::

    >>> cat = Feline2('garfield')
    >>> cat.name
    'Garfield'
    >>> cat.name = 'Pluto'
    >>> cat.name
    'Pluto'

Representación
--------------

.. code:: python

    class Feline:
        ...
        def __repr__(self):
            return "Feline(name={name})".format(name=repr(self._name))

        def __str__(self):
            return self.name

.. testsetup:: *

    class Feline:
        def __init__(self, name):
            self._name = name

        @property
        def name(self):
            return self._name.capitalize()

        def __repr__(self):
            return "Feline(name={name})".format(name=repr(self._name))

        def __str__(self):
            return self.name

.. doctest::

    >>> cat = Feline('garfield')
    >>> cat
    Feline(name='garfield')
    >>> repr(cat)
    "Feline(name='garfield')"
    >>> print(cat)
    Garfield

* ``__repr__``, formal, debug

* ``__str__``, informal, print

Métodos estáticos y de clase
----------------------------

.. code:: python

    class Circle:

        @classmethod
        def create_small_circle(cls):
            return cls(0.001)

        @staticmethod
        def angle_to_rad(grades):
            return 2 * Circle.PI * grades / 360
        ...

.. doctest::

    >>> small_circle = Circle.create_small_circle()
    >>> small_circle.radius
    0.001

.. doctest::

    >>> Circle.angle_to_rad(90)
    1.57
    >>> Circle.angle_to_rad(180)
    3.14

Comparación
-----------

``object.__eq__(self, other)``

Acceso atributos
----------------

``object.__getattr__(self, name)``
``object.__setattr__(self, name, value)``
``object.__delattr__(self, name)``

Emulando contenedores
---------------------

``object.__len__(self)``
``object.__contains__(self, item)``

``object.__getitem__(self, key)``
``object.__setitem__(self, key, value)``
``object.__delitem__(self, key)``

``object.__iter__(self)``

Emulando números
----------------

``object.__add__(self, other)``
``object.__sub__(self, other)``