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 s7commplus package

For S7-1200 and S7-1500 PLCs, the s7commplus package provides a native S7CommPlus protocol client. It supports V1, V2 (TLS), and V3 connections:

from s7commplus import Client

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

The s7 package (legacy S7)

The s7 package implements the classic S7 protocol. It supports S7-300, S7-400, S7-1200 and S7-1500 PLCs via the PUT/GET interface:

from s7 import Client

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

Use s7.Client for S7-300/400 PLCs or when PUT/GET access is enabled on S7-1200/1500. Use s7commplus.Client for native S7CommPlus communication with S7-1200/1500 PLCs.

Note

The snap7 package name continues to work as an alias for s7 and is not deprecated. Existing code using from snap7 import Client does not need to change.

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.