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 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:

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 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.