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import copy
import json
from datetime import date
from pathlib import Path
from typing import Any, Callable, Dict, List, Optional, Type, TypeVar, Union
T = TypeVar("T")
class ComplexSerializableType:
def __init__(self, *args, **kwargs):
pass
# Ideally, the serialized_fields would be an class variable referencing itself, but that it virtually impossible
# to achieve without using metaclasses. Not to complicate the code, we choose instance variable.
@property
def serialized_attributes(self) -> List[str]:
if hasattr(self, "__slots__") and self.__slots__:
return list(self.__slots__)
return list(self.__dict__.keys())
def to_dict(self) -> Dict[str, Any]:
if hasattr(self, "__slots__") and self.__slots__:
return {
key: copy.deepcopy(getattr(self, key)) for key in self.__slots__ if key in self.serialized_attributes
}
return {key: val for key, val in copy.deepcopy(self.__dict__).items() if key in self.serialized_attributes}
@classmethod
def from_dict(cls: Type[T], dct: Dict) -> T:
try:
return cls(**dct)
except TypeError as e:
raise TypeError(f"Dict: {dct} on {cls.__mro__}") from e
def to_json(self, output_path: Optional[Union[str, Path]] = None) -> None:
if not output_path and (not hasattr(self, "json_path") or not self.json_path): # type: ignore
raise ValueError(
f"The object {self} of type {self.__class__} does not have json_path attribute set but to_json() was called without an argument."
)
if not output_path:
output_path = self.json_path # type: ignore
# false positive MyPy warning, cannot be None
with Path(output_path).open("w") as handle: # type: ignore
json.dump(self, handle, indent=4, cls=CustomJSONEncoder, ensure_ascii=False)
@classmethod
def from_json(cls: Type[T], input_path: Union[str, Path]) -> T:
input_path = Path(input_path)
with input_path.open("r") as handle:
obj = json.load(handle, cls=CustomJSONDecoder)
return obj
# Decorator for serialization
def serialize(func: Callable):
def inner_func(*args, **kwargs):
if not args or not issubclass(type(args[0]), ComplexSerializableType):
raise ValueError(
"@serialize decorator is to be used only on instance methods of ComplexSerializableType child classes."
)
update_json = kwargs.pop("update_json", True)
result = func(*args, **kwargs)
if update_json:
args[0].to_json()
return result
return inner_func
class CustomJSONEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj, ComplexSerializableType):
return {**{"_type": type(obj).__name__}, **obj.to_dict()}
if isinstance(obj, dict):
return obj
if isinstance(obj, set):
return {"_type": "Set", "elements": sorted(list(obj))}
if isinstance(obj, frozenset):
return sorted(list(obj))
if isinstance(obj, date):
return str(obj)
if isinstance(obj, Path):
return str(obj)
return super().default(obj)
class CustomJSONDecoder(json.JSONDecoder):
"""
Custom JSONDecoder. Any complex object that should be de-serializable must inherit directly from class
ComplexSerializableType (nested inheritance does not currently work (because x.__subclassess__() prints only direct
subclasses. Any such class must implement methods to_dict() and from_dict(). These are used to drive serialization.
"""
def __init__(self, *args, **kwargs):
json.JSONDecoder.__init__(self, object_hook=self.object_hook, *args, **kwargs)
self.serializable_complex_types = {x.__name__: x for x in ComplexSerializableType.__subclasses__()}
def object_hook(self, obj):
if "_type" in obj and obj["_type"] == "Set":
return set(obj["elements"])
if "_type" in obj and obj["_type"] in self.serializable_complex_types.keys():
complex_type = obj.pop("_type")
return self.serializable_complex_types[complex_type].from_dict(obj)
return obj
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