"""Define a wrapper around an Engine as the Backend class which constructor can initialize Backend instances."""
import attr
from so_magic.data.datapoints_manager import DatapointsManager
from so_magic.data.backend.panda_handling.df_backend import magic_backends
[docs]@attr.s
class Engine:
"""Wrapper of a data engine, a datapoints manager and a datapoints factory.
Instances of this class act as data placeholders (aka data classes) and take at runtime a data engine (eg a set of
pandas-dependent implementations of the "Tabular Data interfaces" defined in so_magic.data.interfaces).
Args:
engine_instance (DataEngine): a data engine represented as a class object (eg class MyClass: pass)
"""
backend_instance = attr.ib(init=True)
backends = attr.ib(init=True, default=attr.Factory(magic_backends))
datapoints_manager = attr.ib(init=False, default=attr.Factory(DatapointsManager))
@property
def backend(self):
"""The Data Engine instance, that this object wraps around.
Returns:
DataEngine: the Data Engine instance object
"""
return self.backend_instance
@backend.setter
def backend(self, engine):
"""Set the Data Engine instance to the input engine object.
Args:
engine (DataEngine): the Data Engine object to set with
"""
self.backend_instance = engine
[docs] @staticmethod
def from_backend(backend_id: str):
engine = Engine(None)
engine.backend = engine.backends.backends[backend_id]
return engine