pickle-mixin

pickle-mixin

|PyPI-License| |PyPI-Version|

Makes un-pickle-able objects pick-able.

Install

You can install it via pip

::

pip install pickle-mixin

Running the tests

After installation, you can test it

::

python -c "import pickle_mixin; pickle_mixin.test()"

as long as you have pytest <http://docs.pytest.org/en/latest/>__.

Usage

Pickle by initialisation

Suppose that you have a class whose objects are un-pickle-able or that
would demand a large amount of disk space or memory to be pickle-able.
``PickleByInit`` class lets you pickle object attributes via object
initialization. Consider the following classes:

.. code:: python

    class Foo(PickleByInit):
        def __init__(self, obj):
            super(Foo, self).__init__()
            self.obj = obj

    class Bar(object):
        def __init__(self, filename):
            self.filename = filename

        def __getstate__(self):
            raise PicklingError

        def init_dict(self):
            return dict(filename=self.filename)

Trying to pickle as follows

.. code:: python

    f = Foo(Bar('file.txt'))
    pickle.dumps(f)

would raise a ``PicklingError``. The following on the other hand would
work:

.. code:: python

    f = Foo(Bar('file.txt'))
    f.set_signature_only_attr('obj')
    pickle.dumps(f)

The un-pickling process of ``f.obj`` attribute happens via object
initialisation, passing the returned dictionary from ``init_dict`` as
keyword arguments to ``Bar.__init__``.

Mixing classes with and without slots

Pickling does not save attributes defined via __slots__ in the following case:

.. code:: python

class Foo(object):
    __slots__ = ['a']

    def __init__(self):
        self.a = 4


class Bar(Foo):
    def __init__(self):
        pass

SlotPickleMixin fixes it:

.. code:: python

class FooMixin(object):
    __slots__ = ['a']

    def __init__(self):
        self.a = 4


class BarMixin(FooMixin, SlotPickleMixin):
    def __init__(self):
        FooMixin.__init__(self)
        SlotPickleMixin.__init__(self)

f = BarMixin()
o = pickle.dumps(f)
f = pickle.loads(o)
assert hasattr(f, 'a')

Authors

• Danilo Horta - https://github.com/Horta

License

This project is licensed under the MIT License - see the LICENSE <LICENSE>__ file for details

.. |PyPI-License| image:: https://img.shields.io/pypi/l/pickle-mixin.svg?style=flat-square :target: https://pypi.python.org/pypi/pickle-mixin/ .. |PyPI-Version| image:: https://img.shields.io/pypi/v/pickle-mixin.svg?style=flat-square :target: https://pypi.python.org/pypi/pickle-mixin/