IOMixin

A mixin class that adds to_file() and from_file() methods to any class, backed by DataZip.

datazip.mixin.IOMixin

Mixin for adding DataZip IO.

Examples:

>>> from io import BytesIO

Create a class that inherits from IOMixin.

>>> class MyClass(IOMixin):
...     pass

Create an instance of the class with many kinds of things in it. As nested as you like.

>>> inst = MyClass()
>>> inst.foo = {"a": 1, "b": (1, 2, 3), "c": [1, 2, 4]}
>>> inst.bar = [1, 2, 3]

The object can now be saved to a file, or buffer for this example.

>>> buffer = BytesIO()
>>> inst.to_file(buffer)
>>> del inst

And we can bring it back, as if it was pickled. Usually.

>>> inst = MyClass.from_file(buffer)
>>> type(inst.bar)
<class 'list'>

>>> inst.foo
{'a': 1, 'b': (1, 2, 3), 'c': [1, 2, 4]}

If your class has funny things in it like lambdas or unserializable objects, you will need to define __getstate__ and __setstate__. If you don't use __slots__ they can be very simple.

>>> from collections import defaultdict
>>> class MyFunnyClass(IOMixin):
...     def __init__(self):
...         self.stuff = defaultdict(lambda: None)
...
...     def __getstate__(self):
...         return self.__dict__ | {"stuff": dict(self.__dict__["stuff"])}
...
...     def __setstate__(self, state):
...         self.__dict__ = state | {
...             "stuff": defaultdict(lambda: None, state["stuff"])
...         }

Instantiate the class and use defaultdict.

>>> inst = MyFunnyClass()
>>> inst.stuff["bar"] = 3
>>> print(inst.stuff["foo"])
None

Dump the object into the buffer and delete the original instance.

>>> buffer = BytesIO()
>>> inst.to_file(buffer)
>>> del inst

Recreate the object from the buffer and confirm it is as it should be.

>>> inst = MyFunnyClass.from_file(buffer)
>>> type(inst.stuff)
<class 'collections.defaultdict'>

>>> print(inst.stuff["foobar"])
None

>>> dict(inst.stuff)
{'bar': 3, 'foo': None, 'foobar': None}

from_file classmethod

from_file(path: Path | str | BytesIO, **kwargs) -> Any

Recreate object fom file or buffer.

Source code in src/datazip/mixin.py

@classmethod
def from_file(cls, path: Path | str | BytesIO, **kwargs) -> Any:
    """Recreate object fom file or buffer."""
    return DataZip.load(path, klass=cls)

to_file

to_file(path: Path | str | BytesIO, compression=ZIP_STORED, clobber=False, **kwargs) -> None

Write object to file or buffer.

Source code in src/datazip/mixin.py

def to_file(
    self,
    path: Path | str | BytesIO,
    compression=ZIP_STORED,
    clobber=False,  # noqa: FBT002
    **kwargs,
) -> None:
    """Write object to file or buffer."""
    DataZip.dump(self, path, compression=compression, clobber=clobber)