Flask & SQLAlchemy & PostgreSQL - In a query can an 'int' be cast to a 'string' to permit use of 'like' - flask-sqlalchemy

Question

Using Flask and SQLAlchemy is it possible to create a query where a column can be cast from a number to a string so that .like() can be used as a filter?
The sample code below illustrates what I'm after, however Test 3 is a broken statement (ie: No attempt at casting so the query fails. Error is below)
Test 1 - demonstrates a standard select
Test 2 - demonstrates a select using like on a string
Can 'test 3' be modified to permit a like on a number?
In PostgreSQL the SQL query would be:
SELECT * FROM mytable WHERE number::varchar like '%2%'
Any assistance gratefully appreciated.
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import Table, Column, Integer, String
app = Flask(__name__)
app.debug = True
app.config.from_pyfile('config.py')
db = SQLAlchemy( app )
class MyTable(db.Model):
'''My Sample Table'''
__tablename__ = 'mytable'
number = db.Column( db.Integer, primary_key = True )
text = db.Column( db.String )
def __repr__(self):
return( 'MyTable( ' + str( self.number ) + ', ' + self.text + ')' )
test_1 = (db.session.query(MyTable)
.all())
print "Test 1 = " + str( test_1 )
test_2 = (db.session.query(MyTable)
.filter( MyTable.text.like( '%orl%' ) )
.all())
print "Test 2 = " + str( test_2 )
test_3 = (db.session.query(MyTable)
.filter( MyTable.number.like( '%2%' ) )
.all())
And the sample data:
=> select * from mytable;
number | text
--------+-------
100 | Hello
20 | World
And the error:
Traceback (most recent call last):
File "sample.py", line 33, in <module>
.filter( MyTable.number.like( '%2%' ) )
File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/query.py", line 2320, in all
return list(self)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/query.py", line 2438, in __iter__
return self._execute_and_instances(context)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/orm/query.py", line 2453, in _execute_and_instances
result = conn.execute(querycontext.statement, self._params)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 729, in execute
return meth(self, multiparams, params)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/sql/elements.py", line 322, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 826, in _execute_clauseelement
compiled_sql, distilled_params
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 958, in _execute_context
context)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 1159, in _handle_dbapi_exception
exc_info
File "/usr/lib64/python2.7/site-packages/sqlalchemy/util/compat.py", line 199, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 951, in _execute_context
context)
File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/default.py", line 436, in do_execute
cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (ProgrammingError) operator does not exist: integer ~~ unknown
LINE 3: WHERE mytable.number LIKE '%2%'
^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
'SELECT mytable.number AS mytable_number, mytable.text AS mytable_text \nFROM mytable \nWHERE mytable.number LIKE %(number_1)s' {'number_1': '%2%'}

Answer 1

Solved. The Query method filter can take an expression, so the solution is:
from sqlalchemy import cast, String
result = (db.session.query(MyTable)
.filter( cast( MyTable.number, String ).like( '%2%' ) )
.all())
With the result:
Test 3 = [MyTable( 20, World)]
Found the information in the SQLAlchemy Query API documentation.