sqlalchemy.dialects.mssql.pymssql

pymssql is a Python module that provides a Python DBAPI interface around FreeTDS.

Modern versions of this driver worked very well with SQL Server and FreeTDS from Linux and were highly recommended. However, pymssql is currently unmaintained and has fallen behind the progress of the Microsoft ODBC driver in its support for newer features of SQL Server. The latest official release of pymssql at the time of this document is version 2.1.4 (August, 2018) and it lacks support for:

1. table-valued parameters (TVPs),
2. datetimeoffset columns using timezone-aware datetime objects (values are sent and retrieved as strings), and
3. encrypted connections (e.g., to Azure SQL), when pymssql is installed from the pre-built wheels. Support for encrypted connections requires building pymssql from source, which can be a nuisance, especially under Windows.

The above features are all supported by mssql+pyodbc when using Microsoft's ODBC Driver for SQL Server (msodbcsql), which is now available for Windows, (several flavors of) Linux, and macOS.