I want to have a primary key id with type uuid in a Postgresql database using SQLAlchemy 1.1.5, connecting to the database with the pg8000 adapter. I used the Backend-agnostic GUID Type recipe from the SQLAlchemy documentation.
When I want to insert into the database, I get the following error
File ".../guid.py", line ???, in process_result_value
return uuid.UUID(value)
File "/usr/lib/python2.7/uuid.py", line 131, in __init__
hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
my model looks like this
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from guid import GUID
import uuid
base = declarative_base()
class Item(base):
__tablename__ = 'item'
id = Column(GUID(), default=uuid.uuid4, nullable=False, unique=True, primary_key=True)
name = Column(String)
description = Column(String)
def __repr__(self):
return "<Item(name='%s', description='%s')>" % (self.name, self.description)
My resource or controller looks like this
data = req.params
item = Item(name=data['name'], description=data['description'])
self.session.add(item)
self.session.commit()
The pg8000
PostgreSQL database adapter is returning a uuid.UUID()
object (see their type mapping documentation, and SQLAlchemy has passed that to the TypeDecorator.process_result_value()
method.
The implementation given in the documentation expected a string, however, so this fails:
>>> import uuid
>>> value = uuid.uuid4()
>>> uuid.UUID(value)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/mjpieters/Development/Library/buildout.python/parts/opt/lib/python2.7/uuid.py", line 133, in __init__
hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'
The quick work-around is to force the value to be a string anyway:
def process_result_value(self, value, dialect):
if value is None:
return value
else:
return uuid.UUID(str(value))
or you can test for the type first:
def process_result_value(self, value, dialect):
if value is None:
return value
else:
if not isinstance(value, uuid.UUID):
value = uuid.UUID(value)
return value
I've submited pull request #403 to fix this in the documentation (since merged).