python-snap7

Python-snap7 is a pure Python S7 communication library for interfacing with Siemens S7 PLCs. It supports Python 3.10+ and runs on Windows, Linux, and macOS without any native dependencies.

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.

The full documentation is available on Read The Docs.

Quick Start

Install using pip:

$ pip install python-snap7

The recommended way to use this library is through the s7 package, which works with all supported PLC models (S7-300, S7-400, S7-1200, S7-1500) and automatically selects the best protocol:

from s7 import Client

client = Client()
client.connect("192.168.1.10", 0, 1)  # auto-detects S7CommPlus vs legacy S7
data = client.db_read(1, 0, 4)
client.disconnect()

The s7.Client automatically tries S7CommPlus first (for S7-1200/1500), and falls back to legacy S7 when needed. No native libraries or platform-specific dependencies are required.

The legacy snap7 package is still available for backwards compatibility:

import snap7

client = snap7.Client()
client.connect("192.168.1.10", 0, 1)
data = client.db_read(1, 0, 4)
client.disconnect()

Version 3.1 -- S7CommPlus Protocol Support (unreleased)

Version 3.1 adds support for the S7CommPlus protocol (up to V2), which is required for communicating with newer Siemens S7-1200 and S7-1500 PLCs that have PUT/GET disabled. This is fully backwards compatible with 3.0.

The s7 package is now the recommended entry point for connecting to any supported S7 PLC. The existing snap7 package continues to work unchanged for legacy S7 connections.

Help us test! Version 3.1 needs more real-world testing before release. If you have access to any of the following PLCs, we would greatly appreciate testing and feedback:

• S7-1200 (any firmware version)
• S7-1500 (any firmware version)
• S7-1500 with TLS enabled
• S7-300
• S7-400
• S7-1200/1500 with PUT/GET disabled (S7CommPlus-only)
• LOGO! 0BA8 and newer

Please report your results -- whether it works or not -- on the issue tracker.

To install the development version:

$ pip install git+https://github.com/gijzelaerr/python-snap7.git@master

Version 3.0 -- Pure Python Rewrite

Version 3.0 was a ground-up rewrite of python-snap7. The library no longer wraps the C snap7 shared library -- instead, the entire S7 protocol stack (TPKT, COTP, and S7) is implemented in pure Python.

• Portability: No more platform-specific shared libraries (.dll, .so, .dylib). Works on any platform that runs Python -- including ARM, Alpine Linux, and other environments where the C library was difficult or impossible to install.
• Easier installation: Just pip install python-snap7. No native dependencies, no compiler toolchains, no manual library setup.
• Easier to extend: New features and protocol support can be added directly in Python.

If you experience issues with 3.0:

1. Please report them on the issue tracker.

2. As a workaround, you can pin to the last pre-3.0 release:

   $ pip install "python-snap7<3"
   

   Documentation for pre-3.0 versions is available at Read The Docs.