python-snap7 3.1.0

Pure Python S7 communication library for Siemens PLCs

About

Python-snap7 is a pure Python S7 communication library for interfacing with Siemens S7 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 is tested with Python 3.10+, on Windows, Linux and OS X.

The full documentation is available on Read The Docs.

Quick Start

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.

Async support:

import asyncio
import snap7

async def main():
    async with snap7.AsyncClient() as client:
        await client.connect("192.168.1.10", 0, 1)
        data = await client.db_read(1, 0, 4)

asyncio.run(main())

What’s New in 3.1

• AsyncClient for asyncio support

• Tag API – read/write by name: client.read_tag("DB1.DBD0:REAL") with PLC4X and nodeS7 dialect support

• Multi-variable read optimizer – merges scattered reads into minimal PDU exchanges

• S7 routing – connect to PLCs on remote subnets via a gateway PLC

• Heartbeat monitoring and auto-reconnect with exponential backoff

• Structured logging with PLC connection context

• PROFINET DCP network discovery

• CLI tools for PLC interaction (pip install "python-snap7[cli]")

• Numerous bug fixes – see CHANGES.md for the full list

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.

Installation

Install using pip:

$ pip install python-snap7

No native libraries or platform-specific dependencies are required — python-snap7 is a pure Python package that works on all platforms.