134 lines
4.4 KiB
Python
134 lines
4.4 KiB
Python
from __future__ import absolute_import, unicode_literals
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class Field(object):
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"""
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Base field for use in :class:`ImmutableObject`. These fields are
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responsible for type checking and other data sanitation in our models.
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For simplicity fields use the Python descriptor protocol to store the
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values in the instance dictionary. Also note that fields are mutable if
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the object they are attached to allow it.
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Default values will be validated with the exception of :class:`None`.
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:param default: default value for field
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:param type: if set the field value must be of this type
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:param choices: if set the field value must be one of these
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"""
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def __init__(self, default=None, type=None, choices=None):
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self._name = None # Set by ImmutableObjectMeta
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self._choices = choices
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self._default = default
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self._type = type
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if self._default is not None:
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self.validate(self._default)
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def validate(self, value):
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"""Validate and possibly modify the field value before assignment"""
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if self._type and not isinstance(value, self._type):
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raise TypeError('Expected %s to be a %s, not %r' %
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(self._name, self._type, value))
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if self._choices and value not in self._choices:
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raise TypeError('Expected %s to be a one of %s, not %r' %
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(self._name, self._choices, value))
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return value
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def __get__(self, instance, owner):
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if not instance:
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return self
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return getattr(instance, '_' + self._name, self._default)
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def __set__(self, instance, value):
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if value is not None:
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value = self.validate(value)
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if value is None or value == self._default:
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self.__delete__(instance)
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else:
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setattr(instance, '_' + self._name, value)
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def __delete__(self, instance):
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if hasattr(instance, '_' + self._name):
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delattr(instance, '_' + self._name)
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class String(Field):
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"""
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Specialized :class:`Field` which is wired up for bytes and unicode.
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:param default: default value for field
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"""
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def __init__(self, default=None):
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# TODO: normalize to unicode?
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# TODO: only allow unicode?
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# TODO: disallow empty strings?
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super(String, self).__init__(type=basestring, default=default)
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class Date(String):
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pass # TODO: make this check for YYYY-MM-DD, YYYY-MM, YYYY using strptime.
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class Identifier(String):
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def validate(self, value):
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return intern(str(super(Identifier, self).validate(value)))
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class URI(Identifier):
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pass # TODO: validate URIs?
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class Integer(Field):
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"""
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:class:`Field` for storing integer numbers.
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:param default: default value for field
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:param min: field value must be larger or equal to this value when set
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:param max: field value must be smaller or equal to this value when set
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"""
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def __init__(self, default=None, min=None, max=None):
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self._min = min
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self._max = max
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super(Integer, self).__init__(type=(int, long), default=default)
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def validate(self, value):
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value = super(Integer, self).validate(value)
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if self._min is not None and value < self._min:
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raise ValueError('Expected %s to be at least %d, not %d' %
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(self._name, self._min, value))
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if self._max is not None and value > self._max:
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raise ValueError('Expected %s to be at most %d, not %d' %
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(self._name, self._max, value))
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return value
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class Collection(Field):
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"""
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:class:`Field` for storing collections of a given type.
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:param type: all items stored in the collection must be of this type
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:param container: the type to store the items in
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"""
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def __init__(self, type, container=tuple):
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super(Collection, self).__init__(type=type, default=container())
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def validate(self, value):
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if isinstance(value, basestring):
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raise TypeError('Expected %s to be a collection of %s, not %r'
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% (self._name, self._type.__name__, value))
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for v in value:
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if not isinstance(v, self._type):
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raise TypeError('Expected %s to be a collection of %s, not %r'
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% (self._name, self._type.__name__, value))
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return self._default.__class__(value) or None
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