Edit File: _pclass.py
import six from pyrsistent._checked_types import (InvariantException, CheckedType, _restore_pickle, store_invariants) from pyrsistent._field_common import (set_fields, check_type, PFIELD_NO_INITIAL, serialize, check_global_invariants) from pyrsistent._transformations import transform def _is_pclass(bases): return len(bases) == 1 and bases[0] == CheckedType class PClassMeta(type): def __new__(mcs, name, bases, dct): set_fields(dct, bases, name='_pclass_fields') store_invariants(dct, bases, '_pclass_invariants', '__invariant__') dct['__slots__'] = ('_pclass_frozen',) + tuple(key for key in dct['_pclass_fields']) # There must only be one __weakref__ entry in the inheritance hierarchy, # lets put it on the top level class. if _is_pclass(bases): dct['__slots__'] += ('__weakref__',) return super(PClassMeta, mcs).__new__(mcs, name, bases, dct) _MISSING_VALUE = object() def _check_and_set_attr(cls, field, name, value, result, invariant_errors): check_type(cls, field, name, value) is_ok, error_code = field.invariant(value) if not is_ok: invariant_errors.append(error_code) else: setattr(result, name, value) @six.add_metaclass(PClassMeta) class PClass(CheckedType): """ A PClass is a python class with a fixed set of specified fields. PClasses are declared as python classes inheriting from PClass. It is defined the same way that PRecords are and behaves like a PRecord in all aspects except that it is not a PMap and hence not a collection but rather a plain Python object. More documentation and examples of PClass usage is available at https://github.com/tobgu/pyrsistent """ def __new__(cls, **kwargs): # Support *args? result = super(PClass, cls).__new__(cls) factory_fields = kwargs.pop('_factory_fields', None) missing_fields = [] invariant_errors = [] for name, field in cls._pclass_fields.items(): if name in kwargs: if factory_fields is None or name in factory_fields: value = field.factory(kwargs[name]) else: value = kwargs[name] _check_and_set_attr(cls, field, name, value, result, invariant_errors) del kwargs[name] elif field.initial is not PFIELD_NO_INITIAL: initial = field.initial() if callable(field.initial) else field.initial _check_and_set_attr( cls, field, name, initial, result, invariant_errors) elif field.mandatory: missing_fields.append('{0}.{1}'.format(cls.__name__, name)) if invariant_errors or missing_fields: raise InvariantException(tuple(invariant_errors), tuple(missing_fields), 'Field invariant failed') if kwargs: raise AttributeError("'{0}' are not among the specified fields for {1}".format( ', '.join(kwargs), cls.__name__)) check_global_invariants(result, cls._pclass_invariants) result._pclass_frozen = True return result def set(self, *args, **kwargs): """ Set a field in the instance. Returns a new instance with the updated value. The original instance remains unmodified. Accepts key-value pairs or single string representing the field name and a value. >>> from pyrsistent import PClass, field >>> class AClass(PClass): ... x = field() ... >>> a = AClass(x=1) >>> a2 = a.set(x=2) >>> a3 = a.set('x', 3) >>> a AClass(x=1) >>> a2 AClass(x=2) >>> a3 AClass(x=3) """ if args: kwargs[args[0]] = args[1] factory_fields = set(kwargs) for key in self._pclass_fields: if key not in kwargs: value = getattr(self, key, _MISSING_VALUE) if value is not _MISSING_VALUE: kwargs[key] = value return self.__class__(_factory_fields=factory_fields, **kwargs) @classmethod def create(cls, kwargs, _factory_fields=None, ignore_extra=False): """ Factory method. Will create a new PClass of the current type and assign the values specified in kwargs. :param ignore_extra: A boolean which when set to True will ignore any keys which appear in kwargs that are not in the set of fields on the PClass. """ if isinstance(kwargs, cls): return kwargs if ignore_extra: kwargs = {k: kwargs[k] for k in cls._pclass_fields if k in kwargs} return cls(_factory_fields=_factory_fields, **kwargs) def serialize(self, format=None): """ Serialize the current PClass using custom serializer functions for fields where such have been supplied. """ result = {} for name in self._pclass_fields: value = getattr(self, name, _MISSING_VALUE) if value is not _MISSING_VALUE: result[name] = serialize(self._pclass_fields[name].serializer, format, value) return result def transform(self, *transformations): """ Apply transformations to the currency PClass. For more details on transformations see the documentation for PMap. Transformations on PClasses do not support key matching since the PClass is not a collection. Apart from that the transformations available for other persistent types work as expected. """ return transform(self, transformations) def __eq__(self, other): if isinstance(other, self.__class__): for name in self._pclass_fields: if getattr(self, name, _MISSING_VALUE) != getattr(other, name, _MISSING_VALUE): return False return True return NotImplemented def __ne__(self, other): return not self == other def __hash__(self): # May want to optimize this by caching the hash somehow return hash(tuple((key, getattr(self, key, _MISSING_VALUE)) for key in self._pclass_fields)) def __setattr__(self, key, value): if getattr(self, '_pclass_frozen', False): raise AttributeError("Can't set attribute, key={0}, value={1}".format(key, value)) super(PClass, self).__setattr__(key, value) def __delattr__(self, key): raise AttributeError("Can't delete attribute, key={0}, use remove()".format(key)) def _to_dict(self): result = {} for key in self._pclass_fields: value = getattr(self, key, _MISSING_VALUE) if value is not _MISSING_VALUE: result[key] = value return result def __repr__(self): return "{0}({1})".format(self.__class__.__name__, ', '.join('{0}={1}'.format(k, repr(v)) for k, v in self._to_dict().items())) def __reduce__(self): # Pickling support data = dict((key, getattr(self, key)) for key in self._pclass_fields if hasattr(self, key)) return _restore_pickle, (self.__class__, data,) def evolver(self): """ Returns an evolver for this object. """ return _PClassEvolver(self, self._to_dict()) def remove(self, name): """ Remove attribute given by name from the current instance. Raises AttributeError if the attribute doesn't exist. """ evolver = self.evolver() del evolver[name] return evolver.persistent() class _PClassEvolver(object): __slots__ = ('_pclass_evolver_original', '_pclass_evolver_data', '_pclass_evolver_data_is_dirty', '_factory_fields') def __init__(self, original, initial_dict): self._pclass_evolver_original = original self._pclass_evolver_data = initial_dict self._pclass_evolver_data_is_dirty = False self._factory_fields = set() def __getitem__(self, item): return self._pclass_evolver_data[item] def set(self, key, value): if self._pclass_evolver_data.get(key, _MISSING_VALUE) is not value: self._pclass_evolver_data[key] = value self._factory_fields.add(key) self._pclass_evolver_data_is_dirty = True return self def __setitem__(self, key, value): self.set(key, value) def remove(self, item): if item in self._pclass_evolver_data: del self._pclass_evolver_data[item] self._factory_fields.discard(item) self._pclass_evolver_data_is_dirty = True return self raise AttributeError(item) def __delitem__(self, item): self.remove(item) def persistent(self): if self._pclass_evolver_data_is_dirty: return self._pclass_evolver_original.__class__(_factory_fields=self._factory_fields, **self._pclass_evolver_data) return self._pclass_evolver_original def __setattr__(self, key, value): if key not in self.__slots__: self.set(key, value) else: super(_PClassEvolver, self).__setattr__(key, value) def __getattr__(self, item): return self[item]
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