Base class for data objects
Project description
Description:
Simple base class for creating data object (it means objects, dedicated to storing data only). It’s a little bit similar to case class from Scala. Using it as base class, You don’t need to take care of data objects boilerplate (like __str__, __eq__, __hash__ methods). Main features: * Objects are considered to be equal based on public fields (method with names started with _ are not took into account) values instead of object identity * __str__ and __repr__ methods return values based on public fields * Static method for creating instances from dictionary. Main difference to dict unpacking is that all non matching keys are ignored and default values are supported * there are two base classes: DataObject and ImmutableDataObject. The second on creates immutable object (so value assigned once to field, cannot be changed)
WARNING: > In future version default behavior may change. It’s still under consideration, whether two different classes with the same set of fields and values should be equal
Install
pip install data_object
Usage
DataObject
from data_object import DataObject class CustomClass(DataObject): class_member = 'XYZ' def __init__(self, foo, bar): self.foo = foo self.bar = bar @property def other(self): return 'ABC'
Str and Repr:
a = CustomClass('a', 'b') print(a) # output: CustomClass: {"bar": b, "class_member": XYZ, "foo": a, "other": ABC} print(repr(a)) # output: CustomClass(bar=b, class_member=XYZ, foo=a, other=ABC)
Equality and Hash
class OtherClass(DataObject): def __init__(self, foo, bar): self.foo = foo self.bar = bar a = CustomClass('a', 'b') b = CustomClass('a', 'b') c = CustomClass('a', 'z') d = OtherClass('a', 'b') a == b # True a == c # False a == d # True z = set() z.add(a) z.add(b) z.add(c) z.add(d) print(z) # output: {CustomClass(bar=z, foo=a), CustomClass(bar=b, foo=a)}
Creating instances from dict
class OtherClass(DataObject): def __init__(self, a, b, c='xyz'): self.a = a self.b = b self.c = c params1 = {'a': 'aaa', 'b': 'bbb', 'c': 'ccc'} params2 = {'a': 'xxx', 'b': 'yyy'} params3 = {'a': 'xxx'} inst1 = OtherClass.from_dict(params1) inst2 = OtherClass.from_dict(params2) inst3 = OtherClass.from_dict(params3, none_if_not_found=True) print(inst1) # output: OtherClass: {"a": aaa, "b": bbb, "c": ccc} print(inst2) # output: OtherClass: {"a": xxx, "b": yyy, "c": xyz} print(inst3) # output: OtherClass: {"a": xxx, "b": None, "c": xyz}
Copy instance (especially useful for immutable objects)
primary_inst = CustomClass(foo='abc', bar='xyz') inst1 = primary_inst.copy() inst2 = primary_inst.copy(bar='aaa') inst3 = primary_inst.copy(bar='aaa', other='some') print(repr(primary_inst)) # output: CustomClass(bar=xyz, foo=abc) print(repr(inst1)) # output: CustomClass(bar=xyz, foo=abc) print(repr(inst2)) # output: CustomClass(bar=aaa, foo=abc) print(repr(inst3)) # output: CustomClass(bar=aaa, foo=abc)
ImmutableDataObject
from data_object import ImmutableDataObject class CustomImmutableClass(ImmutableDataObject): def __init__(self, foo, bar): self.foo = foo self.bar = bar inst = CustomImmutableClass('abc', 'xyz') print(inst) # output: CustomImmutableClass: {"bar": xyz, "foo": abc} inst.foo = 'aaa'
will produce exception:
Traceback (most recent call last): ... data_object.exceptions.ImmutableObjectViolation: Changing attributes not permitted for immutable object
Project details
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