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