I'm using xml
in my postgresql database and I need a custom type could handle xml
data in SQLAlchemy.
So I made XMLType
class communicating with xml.etree
, but It doesn't work as I wished.
here`s the code that I wrote:
import xml.etree.ElementTree as etree
class XMLType(sqlalchemy.types.TypeDecorator):
impl = sqlalchemy.types.UnicodeText
type = etree.Element
def get_col_spec(self):
return 'xml'
def bind_processor(self, dialect):
def process(value):
if value is not None:
return etree.dump(value)
else:
return None
return process
def process_result_value(self, value, dialect):
if value is not None:
value = etree.fromstring(value)
return value
It works well on retrieving values and result processing. but when I tried to insert a row, I get an error(of course, I put the body
as xml.etree.ElementTree.Element
object):
IntegrityError: (IntegrityError) null value in column "body" violates not-null
constraint "INSERT INTO comments (id, author_id, look_id, body, created_at)
VALUES (nextval('object_seq'), %(author_id)s, %(look_id)s, %(body)s, now())
RETURNING comments.id" {'body': None, 'author_id': 1550L, 'look_id': 83293L}
Seeing that the body
value is None
, it's obvious that the binding processor do not work right, but I think I implemented that properly so I don't know what should I do to change the situation.
process_bind_param
gives me the same error.
Where did I go wrong in my code?
ElementTree.dump()
function dumps XML to stream (stdout by default) and returns None
. Use ElementTree.tostring()
or dump it to StringIO
object.
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