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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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