def init_prop(self, obj, value=_Default):
if value is _Default:
value = self.get_default(obj)
new_value = (_none if value is _none else self.type_safe_value(
value, _none_ok=True))
if new_value is _none:
if self.required:
raise exc.PropertyRequired(prop=self)
else:
obj.__dict__[self.name] = new_value
def type_safe_value(self, value, _none_ok=False):
if value is None and self.required and not self.valuetype:
raise exc.PropertyRequired(prop=self)
if self.valuetype and not isinstance(value, self.valuetype):
try:
new_value = self.coerce(value)
except exc.SubtypeCoerceError as e:
# this particular coerce error will be re-caught below,
# unless the coerce method returned None
new_value = e.coerced
except Exception as e:
raise exc.CoerceError(
prop=self,
passed=value,
exc=e,
func=(
"%s constructor" % self.coerce.__name__ if
isinstance(self.coerce, type) else self.coerce
),
valuetype=(
"(" + ", ".join(
x.__name__ for x in self.valuetype
) + ")" if isinstance(self.valuetype, tuple) else
self.valuetype.__name__
),
)
if not isinstance(new_value, self.valuetype):
if _none_ok and new_value is None and not self.required:
# allow coerce functions to return 'None' to silently
# swallow optional properties on initialization
return _none
else:
raise exc.ValueCoercionError(
prop=self,
passed=value,
coerced=new_value,
)
else:
value = new_value
if self.check and not self.check(value):
raise exc.ValueCheckError(
prop=self,
passed=value,
)
return value
def __delete__(self, obj):
"""Checks the property's ``required`` setting, and allows the delete if
it is false"""
if self.required:
raise exc.PropertyRequired(prop=self)
del obj.__dict__[self.name]