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

Connect to any S7 PLC:

import snap7

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

No native libraries or platform-specific dependencies are required.

Version 4.0 -- S7CommPlus & the s7 Package (unreleased)

Note

Version 4.0 is not yet released. Installing with pip install python-snap7 gives you version 3.0, which uses the snap7 package shown above. To try 4.0 early, install from the development branch:

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

S7CommPlus protocol support -- the headline feature of 4.0. S7CommPlus is required for communicating with S7-1200 and S7-1500 PLCs that have PUT/GET disabled. python-snap7 now supports S7CommPlus V1, V2 (with TLS), and V3:

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 new s7 package is the recommended entry point for all new projects. It automatically tries S7CommPlus first (for S7-1200/1500) and falls back to legacy S7 when needed. The existing snap7 package continues to work unchanged.

Other new features in 4.0:

• Command-line interface (s7 read, s7 write, s7 info)
• Partner BSend/BRecv for peer-to-peer communication with S7-1500
• TCP socket optimization (TCP_NODELAY, SO_KEEPALIVE) for lower latency
• S7CommPlus area read/write for M, I, Q, counters, timers (not just DBs)
• Structured logging with PLC connection context for multi-PLC environments

Experimental features (API may change):

• Multi-variable read optimizer -- merges scattered reads into minimal PDU exchanges with parallel dispatch
• S7 routing -- connect to PLCs on remote subnets via a gateway PLC
• Symbolic addressing -- read/write by tag name instead of raw addresses
• Live symbol browsing -- resolve tag names directly from the PLC
• TIA Portal XML import -- import symbol tables from TIA Portal exports

Help us test! If you have access to any Siemens S7 PLC, we would greatly appreciate testing and feedback. Please report results on the issue tracker.

Version 3.0 -- Pure Python Rewrite (current release)

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.