Python-snap7 is a pure Python S7 communication library for interfacing with Siemens S7 PLCs.
Python-snap7 is tested with Python 3.10+, on Windows, Linux and OS X.
The full documentation is available on Read The Docs.
Version 3.0 is a major release that rewrites python-snap7 as a pure Python implementation. The C snap7 library is no longer required.
This release may contain breaking changes. If you experience issues, you can pin to the last pre-3.0 release:
$ pip install "python-snap7<3"
The latest stable pre-3.0 release is version 2.1.0.
This fork (python-snap7-optimized) adds a transparent nodeS7-style read optimization pipeline to the upstream python-snap7 library.
When read_multi_vars() is called with multiple items targeting standard memory
areas (DB, M, I, Q), the library now automatically:
- Sorts requests by area, DB number, and byte offset.
- Merges adjacent or nearby requests (gap ≤ 5 bytes) into contiguous blocks, eliminating redundant reads of overlapping or neighboring addresses.
- Packetizes merged blocks into minimal S7 PDU-sized packets, respecting both request and reply budget limits.
The result is dramatically fewer network round-trips — hundreds of scattered variable reads can collapse into just a few multi-item S7 protocol exchanges.
No API changes required. Existing code using read_multi_vars() benefits
automatically. Counter/Timer areas (CT/TM) fall back to individual reads due to
their different addressing semantics.
New modules:
snap7/optimizer.py— Pure-logic 3-stage pipeline (sort → merge → packetize).- Extended
snap7/s7protocol.py— Multi-item S7 read request building and response parsing. - Extended
snap7/server/__init__.py— Server-side multi-item read support for testing.
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.