Introduction
============

python-snap7 is a pure Python S7 communication library for interfacing
natively with Siemens S7 PLCs. The library implements the complete S7
protocol stack including TPKT (RFC 1006), COTP (ISO 8073), and S7
protocol layers, as well as the S7CommPlus protocol for newer PLCs.

The name "python-snap7" is historical: the library originally started as a
Python wrapper around the `Snap7 <http://snap7.sourceforge.net/>`_ C library.
As of version 3.0, the C library is no longer used, but the name is kept for
backwards compatibility.

python-snap7 requires Python 3.10+ and runs on Windows, macOS and Linux
without any native dependencies.

The ``s7`` package
------------------

The recommended way to use this library is through the ``s7`` package. It
provides a unified client that works with **all supported PLC models** --
S7-300, S7-400, S7-1200 and S7-1500. For newer PLCs (S7-1200/1500) it
automatically tries the S7CommPlus protocol and falls back to legacy S7 when
needed:

.. code-block:: python

   from s7 import Client

   client = Client()
   client.connect("192.168.1.10", 0, 1)
   data = client.db_read(1, 0, 4)
   client.disconnect()

The ``snap7`` package (legacy)
------------------------------

The ``snap7`` package is the original S7 protocol implementation. It remains
fully functional and is kept for backwards compatibility. It supports
S7-300, S7-400, S7-1200 and S7-1500 PLCs via the classic PUT/GET interface.

If you have existing code that uses ``snap7.Client``, it will continue to work
unchanged. For new projects, we recommend using ``s7.Client`` instead.

.. note::

   **Version 3.0 is a complete rewrite.** Previous versions of python-snap7
   were a wrapper around the C snap7 shared library. Starting with version 3.0,
   the entire protocol stack is implemented in pure Python. This eliminates the
   need for platform-specific shared libraries and makes the library portable to
   any platform that runs Python.

   If you experience issues, please report them on the
   `issue tracker <https://github.com/gijzelaerr/python-snap7/issues>`_ with a
   clear description and the version you are using. As a workaround, you can
   install the last pre-3.0 release with ``pip install "python-snap7<3"``.

The project development is centralized on `github <https://github.com/gijzelaerr/python-snap7>`_.