++++++++++++++++++++++
SQLObject and Python 3
++++++++++++++++++++++


.. contents::


Changes between Python 2 and Python 3
-------------------------------------

There are a few changes in the behaviour of SQLObject on Python 3, due to
the changed stings / bytes handling introduced in Python 3.0.

BLOBCol
~~~~~~~

In Python 3, BLOBCol now accepts and returns bytes, rather than strings as it
did in Python 2.

StringCol
~~~~~~~~~

In Python 3, StringCol now accepts arbitrary Unicode strings.

UnicodeCol
~~~~~~~~~~

The dbEncoding parameter to UnicodeCol has no effect in Python 3 code. This
is now handled by the underlying database layer and is no longer exposed
via SQLObject. The parameter is still available for those writing Python 2
compatible code.


Python 3 and MySQL
------------------

SQLObject is tested using mysqlclient_ as the database driver on Python 3.
Note that the default encoding of MySQL databases is *latin1*, which can cause
problems with general Unicode strings. We recommend specifying the character
set as *utf8* when using MySQL to protect against these issues.

.. _mysqlclient: https://pypi.org/project/mysqlclient/


Using databases created with SQLObject and Python 2 in Python 3
---------------------------------------------------------------

For most cases, things should just work as before. The only issues should
around UnicodeCol, as how this is handled has changed.

SQLite
~~~~~~

The Python 3 sqlite driver expects Unicode columns to be encoded using
utf8. Columns created using the default encoding on Python 2 should work fine,
but columns created with a different encoding set using the dbEncoding
parameter may cause problems.

Postgres
~~~~~~~~

Postgres' behaviour is similar to sqlite. Columns created using the
default encoding on Python 2 should work fine, but columns created with a
different encoding set using the dbEncoding may cause problems.

MySQL
~~~~~

For MySQL, the results depend on whether the Python 2 database was using
MySQLdb's Unicode mode or not.

If a character set was specified for the database using the charset parameter,
such as::

   mysql:///localhost/test?charset=latin1

Things should work provided the same character set is specified when using
Python 3.

If a character set wasn't specified, then things may work if the character set
is set to match the dbEncoding parameter used when defining the UnicodeCol.

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