I am using a MS SQL database, together with Python and sqlalchemy. One table has a column defined as 

```
CREATE TABLE MyTable (
    ...
    [address] [varbinary] (16) NULL
    ...

```

The table class `MyTable` is generated by means of table reflection. 
Assigning a string value to `MyTable.address` in my Python code triggers the exception

```
sqlalchemy.exc.StatementError: (builtins.TypeError) string argument without an encoding

```

when writing it to the database. Passing a `bytearray` instead yields the database error

```
(pymssql.OperationalError) (257, 
b'Implicit conversion from data type varchar to varbinary is not allowed. 
Use the CONVERT function to run this query.DB-Lib error message 20018, severity 16 [...]

```

I understand that an encoding is required to store a string in a binary column, but how can I provide that encoding? How else could I write binary data to the database using the ORM capabilities of sqlalchemy?

For I am creating my table classes through reflection, I cannot modify the SQL code directly like described in the answer to [Insert binary file into MSSQL db (varbinary) with python pymssql](https://stackoverflow.com/q/25804024/220000)

Reading the [sqlalchemy documentation on MS SQL](http://docs.sqlalchemy.org/en/latest/dialects/mssql.html) also yielded no solution.