2011-09-09 04:21:32 -07:00

944 lines
32 KiB
Python

from base import (BaseField, ComplexBaseField, ObjectIdField,
ValidationError, get_document)
from queryset import DO_NOTHING
from document import Document, EmbeddedDocument
from connection import _get_db
from operator import itemgetter
import re
import pymongo
import pymongo.dbref
import pymongo.son
import pymongo.binary
import datetime, time
import decimal
import gridfs
__all__ = ['StringField', 'IntField', 'FloatField', 'BooleanField',
'DateTimeField', 'EmbeddedDocumentField', 'ListField', 'DictField',
'ObjectIdField', 'ReferenceField', 'ValidationError', 'MapField',
'DecimalField', 'ComplexDateTimeField', 'URLField',
'GenericReferenceField', 'FileField', 'BinaryField',
'SortedListField', 'EmailField', 'GeoPointField',
'SequenceField']
RECURSIVE_REFERENCE_CONSTANT = 'self'
class StringField(BaseField):
"""A unicode string field.
"""
def __init__(self, regex=None, max_length=None, min_length=None, **kwargs):
self.regex = re.compile(regex) if regex else None
self.max_length = max_length
self.min_length = min_length
super(StringField, self).__init__(**kwargs)
def to_python(self, value):
return unicode(value)
def validate(self, value):
assert isinstance(value, (str, unicode))
if self.max_length is not None and len(value) > self.max_length:
raise ValidationError('String value is too long')
if self.min_length is not None and len(value) < self.min_length:
raise ValidationError('String value is too short')
if self.regex is not None and self.regex.match(value) is None:
message = 'String value did not match validation regex'
raise ValidationError(message)
def lookup_member(self, member_name):
return None
def prepare_query_value(self, op, value):
if not isinstance(op, basestring):
return value
if op.lstrip('i') in ('startswith', 'endswith', 'contains', 'exact'):
flags = 0
if op.startswith('i'):
flags = re.IGNORECASE
op = op.lstrip('i')
regex = r'%s'
if op == 'startswith':
regex = r'^%s'
elif op == 'endswith':
regex = r'%s$'
elif op == 'exact':
regex = r'^%s$'
# escape unsafe characters which could lead to a re.error
value = re.escape(value)
value = re.compile(regex % value, flags)
return value
class URLField(StringField):
"""A field that validates input as an URL.
.. versionadded:: 0.3
"""
URL_REGEX = re.compile(
r'^https?://'
r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?|'
r'localhost|'
r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})'
r'(?::\d+)?'
r'(?:/?|[/?]\S+)$', re.IGNORECASE
)
def __init__(self, verify_exists=False, **kwargs):
self.verify_exists = verify_exists
super(URLField, self).__init__(**kwargs)
def validate(self, value):
if not URLField.URL_REGEX.match(value):
raise ValidationError('Invalid URL: %s' % value)
if self.verify_exists:
import urllib2
try:
request = urllib2.Request(value)
response = urllib2.urlopen(request)
except Exception, e:
message = 'This URL appears to be a broken link: %s' % e
raise ValidationError(message)
class EmailField(StringField):
"""A field that validates input as an E-Mail-Address.
.. versionadded:: 0.4
"""
EMAIL_REGEX = re.compile(
r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*" # dot-atom
r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-011\013\014\016-\177])*"' # quoted-string
r')@(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?$', re.IGNORECASE # domain
)
def validate(self, value):
if not EmailField.EMAIL_REGEX.match(value):
raise ValidationError('Invalid Mail-address: %s' % value)
class IntField(BaseField):
"""An integer field.
"""
def __init__(self, min_value=None, max_value=None, **kwargs):
self.min_value, self.max_value = min_value, max_value
super(IntField, self).__init__(**kwargs)
def to_python(self, value):
return int(value)
def validate(self, value):
try:
value = int(value)
except:
raise ValidationError('%s could not be converted to int' % value)
if self.min_value is not None and value < self.min_value:
raise ValidationError('Integer value is too small')
if self.max_value is not None and value > self.max_value:
raise ValidationError('Integer value is too large')
def prepare_query_value(self, op, value):
return int(value)
class FloatField(BaseField):
"""An floating point number field.
"""
def __init__(self, min_value=None, max_value=None, **kwargs):
self.min_value, self.max_value = min_value, max_value
super(FloatField, self).__init__(**kwargs)
def to_python(self, value):
return float(value)
def validate(self, value):
if isinstance(value, int):
value = float(value)
assert isinstance(value, float)
if self.min_value is not None and value < self.min_value:
raise ValidationError('Float value is too small')
if self.max_value is not None and value > self.max_value:
raise ValidationError('Float value is too large')
def prepare_query_value(self, op, value):
return float(value)
class DecimalField(BaseField):
"""A fixed-point decimal number field.
.. versionadded:: 0.3
"""
def __init__(self, min_value=None, max_value=None, **kwargs):
self.min_value, self.max_value = min_value, max_value
super(DecimalField, self).__init__(**kwargs)
def to_python(self, value):
if not isinstance(value, basestring):
value = unicode(value)
return decimal.Decimal(value)
def to_mongo(self, value):
return unicode(value)
def validate(self, value):
if not isinstance(value, decimal.Decimal):
if not isinstance(value, basestring):
value = str(value)
try:
value = decimal.Decimal(value)
except Exception, exc:
raise ValidationError('Could not convert to decimal: %s' % exc)
if self.min_value is not None and value < self.min_value:
raise ValidationError('Decimal value is too small')
if self.max_value is not None and value > self.max_value:
raise ValidationError('Decimal value is too large')
class BooleanField(BaseField):
"""A boolean field type.
.. versionadded:: 0.1.2
"""
def to_python(self, value):
return bool(value)
def validate(self, value):
assert isinstance(value, bool)
class DateTimeField(BaseField):
"""A datetime field.
Note: Microseconds are rounded to the nearest millisecond.
Pre UTC microsecond support is effecively broken.
Use :class:`~mongoengine.fields.ComplexDateTimeField` if you
need accurate microsecond support.
"""
def validate(self, value):
assert isinstance(value, (datetime.datetime, datetime.date))
def to_mongo(self, value):
return self.prepare_query_value(None, value)
def prepare_query_value(self, op, value):
if value is None:
return value
if isinstance(value, datetime.datetime):
return value
if isinstance(value, datetime.date):
return datetime.datetime(value.year, value.month, value.day)
# Attempt to parse a datetime:
# value = smart_str(value)
# split usecs, because they are not recognized by strptime.
if '.' in value:
try:
value, usecs = value.split('.')
usecs = int(usecs)
except ValueError:
return None
else:
usecs = 0
kwargs = {'microsecond': usecs}
try: # Seconds are optional, so try converting seconds first.
return datetime.datetime(*time.strptime(value, '%Y-%m-%d %H:%M:%S')[:6],
**kwargs)
except ValueError:
try: # Try without seconds.
return datetime.datetime(*time.strptime(value, '%Y-%m-%d %H:%M')[:5],
**kwargs)
except ValueError: # Try without hour/minutes/seconds.
try:
return datetime.datetime(*time.strptime(value, '%Y-%m-%d')[:3],
**kwargs)
except ValueError:
return None
class ComplexDateTimeField(StringField):
"""
ComplexDateTimeField handles microseconds exactly instead of rounding
like DateTimeField does.
Derives from a StringField so you can do `gte` and `lte` filtering by
using lexicographical comparison when filtering / sorting strings.
The stored string has the following format:
YYYY,MM,DD,HH,MM,SS,NNNNNN
Where NNNNNN is the number of microseconds of the represented `datetime`.
The `,` as the separator can be easily modified by passing the `separator`
keyword when initializing the field.
.. versionadded:: 0.5
"""
def __init__(self, separator=',', **kwargs):
self.names = ['year', 'month', 'day', 'hour', 'minute', 'second',
'microsecond']
self.separtor = separator
super(ComplexDateTimeField, self).__init__(**kwargs)
def _leading_zero(self, number):
"""
Converts the given number to a string.
If it has only one digit, a leading zero so as it has always at least
two digits.
"""
if int(number) < 10:
return "0%s" % number
else:
return str(number)
def _convert_from_datetime(self, val):
"""
Convert a `datetime` object to a string representation (which will be
stored in MongoDB). This is the reverse function of
`_convert_from_string`.
>>> a = datetime(2011, 6, 8, 20, 26, 24, 192284)
>>> RealDateTimeField()._convert_from_datetime(a)
'2011,06,08,20,26,24,192284'
"""
data = []
for name in self.names:
data.append(self._leading_zero(getattr(val, name)))
return ','.join(data)
def _convert_from_string(self, data):
"""
Convert a string representation to a `datetime` object (the object you
will manipulate). This is the reverse function of
`_convert_from_datetime`.
>>> a = '2011,06,08,20,26,24,192284'
>>> ComplexDateTimeField()._convert_from_string(a)
datetime.datetime(2011, 6, 8, 20, 26, 24, 192284)
"""
data = data.split(',')
data = map(int, data)
values = {}
for i in range(7):
values[self.names[i]] = data[i]
return datetime.datetime(**values)
def __get__(self, instance, owner):
data = super(ComplexDateTimeField, self).__get__(instance, owner)
if data == None:
return datetime.datetime.now()
return self._convert_from_string(data)
def __set__(self, instance, value):
value = self._convert_from_datetime(value)
return super(ComplexDateTimeField, self).__set__(instance, value)
def validate(self, value):
if not isinstance(value, datetime.datetime):
raise ValidationError('Only datetime objects may used in a \
ComplexDateTimeField')
def to_python(self, value):
return self._convert_from_string(value)
def to_mongo(self, value):
return self._convert_from_datetime(value)
def prepare_query_value(self, op, value):
return self._convert_from_datetime(value)
class EmbeddedDocumentField(BaseField):
"""An embedded document field. Only valid values are subclasses of
:class:`~mongoengine.EmbeddedDocument`.
"""
def __init__(self, document_type, **kwargs):
if not isinstance(document_type, basestring):
if not issubclass(document_type, EmbeddedDocument):
raise ValidationError('Invalid embedded document class '
'provided to an EmbeddedDocumentField')
self.document_type_obj = document_type
super(EmbeddedDocumentField, self).__init__(**kwargs)
@property
def document_type(self):
if isinstance(self.document_type_obj, basestring):
if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
self.document_type_obj = self.owner_document
else:
self.document_type_obj = get_document(self.document_type_obj)
return self.document_type_obj
def to_python(self, value):
if not isinstance(value, self.document_type):
return self.document_type._from_son(value)
return value
def to_mongo(self, value):
if not isinstance(value, self.document_type):
return value
return self.document_type.to_mongo(value)
def validate(self, value):
"""Make sure that the document instance is an instance of the
EmbeddedDocument subclass provided when the document was defined.
"""
# Using isinstance also works for subclasses of self.document
if not isinstance(value, self.document_type):
raise ValidationError('Invalid embedded document instance '
'provided to an EmbeddedDocumentField')
self.document_type.validate(value)
def lookup_member(self, member_name):
return self.document_type._fields.get(member_name)
def prepare_query_value(self, op, value):
return self.to_mongo(value)
class ListField(ComplexBaseField):
"""A list field that wraps a standard field, allowing multiple instances
of the field to be used as a list in the database.
"""
# ListFields cannot be indexed with _types - MongoDB doesn't support this
_index_with_types = False
def __init__(self, field=None, **kwargs):
self.field = field
kwargs.setdefault('default', lambda: [])
super(ListField, self).__init__(**kwargs)
def validate(self, value):
"""Make sure that a list of valid fields is being used.
"""
if not isinstance(value, (list, tuple)):
raise ValidationError('Only lists and tuples may be used in a '
'list field')
super(ListField, self).validate(value)
def prepare_query_value(self, op, value):
if self.field:
if op in ('set', 'unset') and (not isinstance(value, basestring)
and hasattr(value, '__iter__')):
return [self.field.prepare_query_value(op, v) for v in value]
return self.field.prepare_query_value(op, value)
return super(ListField, self).prepare_query_value(op, value)
class SortedListField(ListField):
"""A ListField that sorts the contents of its list before writing to
the database in order to ensure that a sorted list is always
retrieved.
.. versionadded:: 0.4
"""
_ordering = None
def __init__(self, field, **kwargs):
if 'ordering' in kwargs.keys():
self._ordering = kwargs.pop('ordering')
super(SortedListField, self).__init__(field, **kwargs)
def to_mongo(self, value):
value = super(SortedListField, self).to_mongo(value)
if self._ordering is not None:
return sorted(value, key=itemgetter(self._ordering))
return sorted(value)
class DictField(ComplexBaseField):
"""A dictionary field that wraps a standard Python dictionary. This is
similar to an embedded document, but the structure is not defined.
.. versionadded:: 0.3
.. versionchanged:: 0.5 - Can now handle complex / varying types of data
"""
def __init__(self, basecls=None, field=None, *args, **kwargs):
self.field = field
self.basecls = basecls or BaseField
assert issubclass(self.basecls, BaseField)
kwargs.setdefault('default', lambda: {})
super(DictField, self).__init__(*args, **kwargs)
def validate(self, value):
"""Make sure that a list of valid fields is being used.
"""
if not isinstance(value, dict):
raise ValidationError('Only dictionaries may be used in a '
'DictField')
if any(('.' in k or '$' in k) for k in value):
raise ValidationError('Invalid dictionary key name - keys may not '
'contain "." or "$" characters')
super(DictField, self).validate(value)
def lookup_member(self, member_name):
return DictField(basecls=self.basecls, db_field=member_name)
def prepare_query_value(self, op, value):
match_operators = ['contains', 'icontains', 'startswith',
'istartswith', 'endswith', 'iendswith',
'exact', 'iexact']
if op in match_operators and isinstance(value, basestring):
return StringField().prepare_query_value(op, value)
return super(DictField, self).prepare_query_value(op, value)
class MapField(DictField):
"""A field that maps a name to a specified field type. Similar to
a DictField, except the 'value' of each item must match the specified
field type.
.. versionadded:: 0.5
"""
def __init__(self, field=None, *args, **kwargs):
if not isinstance(field, BaseField):
raise ValidationError('Argument to MapField constructor must be '
'a valid field')
super(MapField, self).__init__(field=field, *args, **kwargs)
class ReferenceField(BaseField):
"""A reference to a document that will be automatically dereferenced on
access (lazily).
Use the `reverse_delete_rule` to handle what should happen if the document
the field is referencing is deleted.
The options are:
* DO_NOTHING - don't do anything (default).
* NULLIFY - Updates the reference to null.
* CASCADE - Deletes the documents associated with the reference.
* DENY - Prevent the deletion of the reference object.
.. versionchanged:: 0.5 added `reverse_delete_rule`
"""
def __init__(self, document_type, reverse_delete_rule=DO_NOTHING, **kwargs):
"""Initialises the Reference Field.
:param reverse_delete_rule: Determines what to do when the referring
object is deleted
"""
if not isinstance(document_type, basestring):
if not issubclass(document_type, (Document, basestring)):
raise ValidationError('Argument to ReferenceField constructor '
'must be a document class or a string')
self.document_type_obj = document_type
self.reverse_delete_rule = reverse_delete_rule
super(ReferenceField, self).__init__(**kwargs)
@property
def document_type(self):
if isinstance(self.document_type_obj, basestring):
if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
self.document_type_obj = self.owner_document
else:
self.document_type_obj = get_document(self.document_type_obj)
return self.document_type_obj
def __get__(self, instance, owner):
"""Descriptor to allow lazy dereferencing.
"""
if instance is None:
# Document class being used rather than a document object
return self
# Get value from document instance if available
value = instance._data.get(self.name)
# Dereference DBRefs
if isinstance(value, (pymongo.dbref.DBRef)):
value = _get_db().dereference(value)
if value is not None:
instance._data[self.name] = self.document_type._from_son(value)
return super(ReferenceField, self).__get__(instance, owner)
def to_mongo(self, document):
id_field_name = self.document_type._meta['id_field']
id_field = self.document_type._fields[id_field_name]
if isinstance(document, Document):
# We need the id from the saved object to create the DBRef
id_ = document.id
if id_ is None:
raise ValidationError('You can only reference documents once '
'they have been saved to the database')
else:
id_ = document
id_ = id_field.to_mongo(id_)
collection = self.document_type._get_collection_name()
return pymongo.dbref.DBRef(collection, id_)
def prepare_query_value(self, op, value):
return self.to_mongo(value)
def validate(self, value):
assert isinstance(value, (self.document_type, pymongo.dbref.DBRef))
if isinstance(value, Document) and value.id is None:
raise ValidationError('You can only reference documents once '
'they have been saved to the database')
def lookup_member(self, member_name):
return self.document_type._fields.get(member_name)
class GenericReferenceField(BaseField):
"""A reference to *any* :class:`~mongoengine.document.Document` subclass
that will be automatically dereferenced on access (lazily).
..note :: Any documents used as a generic reference must be registered in the
document registry. Importing the model will automatically register it.
.. versionadded:: 0.3
"""
def __get__(self, instance, owner):
if instance is None:
return self
value = instance._data.get(self.name)
if isinstance(value, (dict, pymongo.son.SON)):
instance._data[self.name] = self.dereference(value)
return super(GenericReferenceField, self).__get__(instance, owner)
def validate(self, value):
if not isinstance(value, (Document, pymongo.dbref.DBRef)):
raise ValidationError('GenericReferences can only contain documents')
# We need the id from the saved object to create the DBRef
if isinstance(value, Document) and value.id is None:
raise ValidationError('You can only reference documents once '
'they have been saved to the database')
def dereference(self, value):
doc_cls = get_document(value['_cls'])
reference = value['_ref']
doc = _get_db().dereference(reference)
if doc is not None:
doc = doc_cls._from_son(doc)
return doc
def to_mongo(self, document):
if document is None:
return None
id_field_name = document.__class__._meta['id_field']
id_field = document.__class__._fields[id_field_name]
if isinstance(document, Document):
# We need the id from the saved object to create the DBRef
id_ = document.id
if id_ is None:
raise ValidationError('You can only reference documents once '
'they have been saved to the database')
else:
id_ = document
id_ = id_field.to_mongo(id_)
collection = document._get_collection_name()
ref = pymongo.dbref.DBRef(collection, id_)
return {'_cls': document._class_name, '_ref': ref}
def prepare_query_value(self, op, value):
return self.to_mongo(value)
class BinaryField(BaseField):
"""A binary data field.
"""
def __init__(self, max_bytes=None, **kwargs):
self.max_bytes = max_bytes
super(BinaryField, self).__init__(**kwargs)
def to_mongo(self, value):
return pymongo.binary.Binary(value)
def to_python(self, value):
# Returns str not unicode as this is binary data
return str(value)
def validate(self, value):
assert isinstance(value, str)
if self.max_bytes is not None and len(value) > self.max_bytes:
raise ValidationError('Binary value is too long')
class GridFSError(Exception):
pass
class GridFSProxy(object):
"""Proxy object to handle writing and reading of files to and from GridFS
.. versionadded:: 0.4
.. versionchanged:: 0.5 - added optional size param to read
"""
def __init__(self, grid_id=None, key=None, instance=None):
self.fs = gridfs.GridFS(_get_db()) # Filesystem instance
self.newfile = None # Used for partial writes
self.grid_id = grid_id # Store GridFS id for file
self.gridout = None
self.key = key
self.instance = instance
def __getattr__(self, name):
obj = self.get()
if name in dir(obj):
return getattr(obj, name)
raise AttributeError
def __get__(self, instance, value):
return self
def __nonzero__(self):
return bool(self.grid_id)
def get(self, id=None):
if id:
self.grid_id = id
if self.grid_id is None:
return None
try:
if self.gridout is None:
self.gridout = self.fs.get(self.grid_id)
return self.gridout
except:
# File has been deleted
return None
def new_file(self, **kwargs):
self.newfile = self.fs.new_file(**kwargs)
self.grid_id = self.newfile._id
def put(self, file_obj, **kwargs):
if self.grid_id:
raise GridFSError('This document already has a file. Either delete '
'it or call replace to overwrite it')
self.grid_id = self.fs.put(file_obj, **kwargs)
self._mark_as_changed()
def write(self, string):
if self.grid_id:
if not self.newfile:
raise GridFSError('This document already has a file. Either '
'delete it or call replace to overwrite it')
else:
self.new_file()
self.newfile.write(string)
def writelines(self, lines):
if not self.newfile:
self.new_file()
self.grid_id = self.newfile._id
self.newfile.writelines(lines)
def read(self, size=-1):
try:
return self.get().read(size)
except:
return None
def delete(self):
# Delete file from GridFS, FileField still remains
self.fs.delete(self.grid_id)
self.grid_id = None
self.gridout = None
self._mark_as_changed()
def replace(self, file_obj, **kwargs):
self.delete()
self.put(file_obj, **kwargs)
def close(self):
if self.newfile:
self.newfile.close()
def _mark_as_changed(self):
"""Inform the instance that `self.key` has been changed"""
if self.instance:
self.instance._mark_as_changed(self.key)
class FileField(BaseField):
"""A GridFS storage field.
.. versionadded:: 0.4
.. versionchanged:: 0.5 added optional size param for read
"""
def __init__(self, **kwargs):
super(FileField, self).__init__(**kwargs)
def __get__(self, instance, owner):
if instance is None:
return self
# Check if a file already exists for this model
grid_file = instance._data.get(self.name)
self.grid_file = grid_file
if isinstance(self.grid_file, GridFSProxy):
if not self.grid_file.key:
self.grid_file.key = self.name
self.grid_file.instance = instance
return self.grid_file
return GridFSProxy(key=self.name, instance=instance)
def __set__(self, instance, value):
key = self.name
if isinstance(value, file) or isinstance(value, str):
# using "FileField() = file/string" notation
grid_file = instance._data.get(self.name)
# If a file already exists, delete it
if grid_file:
try:
grid_file.delete()
except:
pass
# Create a new file with the new data
grid_file.put(value)
else:
# Create a new proxy object as we don't already have one
instance._data[key] = GridFSProxy(key=key, instance=instance)
instance._data[key].put(value)
else:
instance._data[key] = value
instance._mark_as_changed(key)
def to_mongo(self, value):
# Store the GridFS file id in MongoDB
if isinstance(value, GridFSProxy) and value.grid_id is not None:
return value.grid_id
return None
def to_python(self, value):
if value is not None:
return GridFSProxy(value)
def validate(self, value):
if value.grid_id is not None:
assert isinstance(value, GridFSProxy)
assert isinstance(value.grid_id, pymongo.objectid.ObjectId)
class GeoPointField(BaseField):
"""A list storing a latitude and longitude.
.. versionadded:: 0.4
"""
_geo_index = True
def validate(self, value):
"""Make sure that a geo-value is of type (x, y)
"""
if not isinstance(value, (list, tuple)):
raise ValidationError('GeoPointField can only accept tuples or '
'lists of (x, y)')
if not len(value) == 2:
raise ValidationError('Value must be a two-dimensional point.')
if (not isinstance(value[0], (float, int)) and
not isinstance(value[1], (float, int))):
raise ValidationError('Both values in point must be float or int.')
class SequenceField(IntField):
"""Provides a sequental counter.
..note:: Although traditional databases often use increasing sequence
numbers for primary keys. In MongoDB, the preferred approach is to
use Object IDs instead. The concept is that in a very large
cluster of machines, it is easier to create an object ID than have
global, uniformly increasing sequence numbers.
.. versionadded:: 0.5
"""
def __init__(self, collection_name=None, *args, **kwargs):
self.collection_name = collection_name or 'mongoengine.counters'
return super(SequenceField, self).__init__(*args, **kwargs)
def generate_new_value(self):
"""
Generate and Increment the counter
"""
sequence_id = "{0}.{1}".format(self.owner_document._get_collection_name(),
self.name)
collection = _get_db()[self.collection_name]
counter = collection.find_and_modify(query={"_id": sequence_id},
update={"$inc": {"next": 1}},
new=True,
upsert=True)
return counter['next']
def __get__(self, instance, owner):
if instance is None:
return self
if not instance._data:
return
value = instance._data.get(self.name)
if not value and instance._initialised:
value = self.generate_new_value()
instance._data[self.name] = value
instance._mark_as_changed(self.name)
return value
def __set__(self, instance, value):
if value is None and instance._initialised:
value = self.generate_new_value()
return super(SequenceField, self).__set__(instance, value)
def to_python(self, value):
if value is None:
value = self.generate_new_value()
return value