Encoding error with sqlalchemy and postgresql

Question

I'm using pyramid for a web application with a postgres database, wtforms, sqlalchemy and jinja2 and I'm having this error when the application try to get the issues types from database to fill a select field with wtforms:

Error: 'ascii' codec can't decode byte 0xc3 in position 5: ordinal not in range(128)

this is the issue types table into model.py:

class Mixin(object):
    id = Column(Integer, primary_key=True, autoincrement=True)
    created = Column(DateTime())
    modified = Column(DateTime())

    __table_args__ = {
        'mysql_engine': 'InnoDB',
        'mysql_charset': 'utf8'
    }
    __mapper_args__ = {'extension': BaseExtension()}

class IssueType(Mixin, Base):
    __tablename__ = "ma_issue_types"
    name = Column(Unicode(40), nullable=False)

    def __init__(self, name):
        self.name = name

Into bd I have this:

# select name from ma_issue_types where id = 3;
name    
------------
Teléfono

this is the part where the error occurs

# -*- coding: utf-8 -*-

from issuemall.models import DBSession, IssueType


class IssueTypeDao(object):

    def getAll(self):
        dbsession = DBSession()
        return dbsession.query(IssueType).all() #HERE THROWS THE ERROR

this is the Traceback

Traceback (most recent call last):
  File "/issueMall/issuemall/controller/issueRegisterController.py", line 16, in issue_register
    form = IssueRegisterForm(request.POST)
  File "/env/lib/python2.7/site-packages/wtforms/form.py", line 178, in __call__
    return type.__call__(cls, *args, **kwargs)
  File "/env/lib/python2.7/site-packages/wtforms/form.py", line 224, in __init__
    super(Form, self).__init__(self._unbound_fields, prefix=prefix)
  File "/env/lib/python2.7/site-packages/wtforms/form.py", line 39, in __init__
    field = unbound_field.bind(form=self, name=name, prefix=prefix, translations=translations)
  File "/env/lib/python2.7/site-packages/wtforms/fields/core.py", line 301, in bind
    return self.field_class(_form=form, _prefix=prefix, _name=name, _translations=translations, *self.args, **dict(self.kwargs, **kwargs))
  File "/issueMall/issuemall/form/generalForm.py", line 11, in __init__
    types = issueTypeDao.getAll()
  File "/issueMall/issuemall/dao/master/issueTypeDao.py", line 11, in getAll
    return self.__dbsession.query(IssueType).all()
  File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 2115, in all
    return list(self)
  File "build/bdist.linux-x86_64/egg/sqlalchemy/orm/query.py", line 2341, in instances
    fetch = cursor.fetchall()
  File "build/bdist.linux-x86_64/egg/sqlalchemy/engine/base.py", line 3205, in fetchall
    l = self.process_rows(self._fetchall_impl())
  File "build/bdist.linux-x86_64/egg/sqlalchemy/engine/base.py", line 3172, in _fetchall_impl
    return self.cursor.fetchall()
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 5: ordinal not in range(128)

I try this, but it did not work ascii as default encoding in python

and I try something like this, but it did not work

gae python ascii codec cant decode byte

return dbsession.query(IssueType.id, IssueType.name.encode('utf-8')).all() #or decode('utf-8')

Answer 1

You need to configure Psycopg2's client encoding. See the SQLAlchemy documentation:

By default, the psycopg2 driver uses the psycopg2.extensions.UNICODE extension, such that the DBAPI receives and returns all strings as Python Unicode objects directly - SQLAlchemy passes these values through without change. Psycopg2 here will encode/decode string values based on the current “client encoding” setting; by default this is the value in the postgresql.conf file, which often defaults to SQL_ASCII. Typically, this can be changed to utf-8, as a more useful default:

#client_encoding = sql_ascii # actually, defaults to database
                             # encoding
client_encoding = utf8

A second way to affect the client encoding is to set it within Psycopg2 locally. SQLAlchemy will call psycopg2’s set_client_encoding() method (see: http://initd.org/psycopg/docs/connection.html#connection.set_client_encoding) on all new connections based on the value passed to create_engine() using the client_encoding parameter:

engine = create_engine("postgresql://user:pass@host/dbname", client_encoding='utf8')

This overrides the encoding specified in the Postgresql client configuration.

The client_encoding parameter can be specified as a query string in the engine URL:

 postgresql://user:pass@host/dbname?client_encoding=utf8

Answer 2

I use mysql and set the charset like this. It works for me.

from sqlalchemy import create_engine
from sqlalchemy.engine.url import URL

db_url = {
    'database': 'db_name',
    'drivername': 'mysql',
    'username': 'username',
    'password': 'mypassword',
    'host': '127.0.0.1',
    'query': {'charset': 'utf8'},
}

engine = create_engine(URL(**db_url), encoding="utf8")