3.1.0

python-snap7 3.1.0

A feature-rich release adding async support, a CLI, symbolic addressing, network discovery, and many quality-of-life improvements to the pure-Python S7 library introduced in 3.0.

New features

• AsyncClient — full asyncio-based client for non-blocking PLC communication (#593)
• CLI tools — snap7 command-line interface for PLC interaction; install with pip install "python-snap7[cli]" (#631)
• Typed DB access — convenience methods for reading/writing common S7 data types (BOOL, INT, REAL, etc.) directly (#632)
• PROFINET DCP discovery — discover PLCs on the local network without knowing their IP addresses (#634)
• Heartbeat & auto-reconnect — connection monitoring with configurable heartbeat interval and exponential-backoff reconnection (#635)
• Symbolic addressing (Tags) — read/write PLC variables by name using a unified Tag API with PLC4X and nodeS7 dialect support (#638, #697, #701)
• S7 routing — access PLCs behind gateways across multiple subnets (#639)
• Multi-variable read optimizer — automatically batch multiple reads into minimal PDU exchanges (#641)
• Structured logging — PLC connection context (host/rack/slot) attached to log records, with JSON formatter (#688)
• Diagnostic buffer & data-change subscriptions — read the PLC diagnostic buffer and subscribe to variable changes (#690)
• Block transfer & CPU state control — upload/download blocks, start/stop/hot-start/cold-start the PLC (#693)
• Demo subcommand — snap7 demo starts a live server exposing real host metrics for quick testing (#704)

Bug fixes

• Fix get_cpu_info and S7SZL.__str__ (#692)
• Fix server SZL 0x001C response to match real PLC format (#694)
• Fix AttributeError from __del__ during interpreter shutdown (#707)
• Use connection_type in TSAP composition during connect (#766)
• Accept memoryview in setter/getter type annotations (#647)
• Zero-pad milliseconds in get_time so 3 ms reads as ".003" (#716)
• Use proper PI service PDU format for PLC control commands (#733, #743)
• Set TCP_NODELAY and SO_KEEPALIVE on all S7 sockets (#677)
• Backport robustness improvements from python-s7comm (#580)
• Add get_ulint and get_lint to snap7.util exports (#652)
• Fix async get_cpu_info and extract shared SZL/block parsers (#702)
• Fix demo primary-IP guess with VPN/tunnel interfaces (#708)

Other improvements

• Property-based testing with Hypothesis (#636)
• Improved documentation with intersphinx cross-references and restructured API docs
• Full type annotations with mypy strict mode (no type: ignore needed)
• Python 3.10–3.14 support

Upgrading from 3.0

This is a backwards-compatible release. All existing 3.0 code should work without changes. New features are additive.

If you experience any issues, please report them on the issue tracker.

3.0.0 — Pure Python Rewrite

python-snap7 3.0.0 — Pure Python Rewrite

This is a major release that completely rewrites python-snap7 as a pure Python S7 communication library. The C snap7 shared library is no longer used — the entire protocol stack (TPKT, COTP, and S7) is now implemented in pure Python.

The name "python-snap7" is historical — the library originally started as a Python wrapper around the Snap7 C library. As of this release, the C library is no longer needed, but the name is kept for backwards compatibility.

What's new

• Pure Python implementation — no native dependencies, no shared libraries
• Works everywhere — any platform that runs Python 3.10+, including ARM, Alpine Linux, and other environments where the C library was difficult or impossible to install
• Easier to extend — new features and protocol support can be added directly in Python
• Complete TPKT (RFC 1006) and COTP (ISO 8073) transport layer implementation
• Native S7 protocol PDU encoding/decoding
• Pure Python server implementation for testing and simulation
• Full type annotations with mypy strict mode
• CLI interface for running an S7 server emulator (pip install "python-snap7[cli]")

Breaking changes

This release completely breaks with the previous approach of wrapping the C snap7 shared library. While the public API is largely the same, this is a fundamental change under the hood. If you experience issues:

1. Please report them on the issue tracker with a clear description and the version you are using (python -c "import snap7; print(snap7.__version__)")
2. As a workaround, pin to the last pre-3.0 release: pip install "python-snap7<3"

Thanks

Special thanks to the following people for testing, reporting issues, and providing feedback during the 3.0 development:

• @lupaulus — extensive testing and bug reports
• @spreeker — testing and feedback
• @nikteliy — review and feedback on the rewrite
• @amorelettronico — testing
• @razour08 — testing
• @core-engineering — bug reports
• @AndreasScharf — bug reports
• @Robatronic — bug reports
• @hirotasoshu — feedback
• @PoitrasJ — bug reports

2.1.1

Fix Read the Docs build configuration for pre-3.0 documentation.

• Fix .readthedocs.yaml to install from pyproject.toml extras instead of missing requirements-dev.txt
• Add mock imports in doc/conf.py so autodoc works without the native snap7 C library on RTD
• Use sphinx_rtd_theme for consistent styling

v2.1.0

What's Changed

Bug Fixes

• Fix PLC setter functions for memoryview compatibility (#575)
• Cache error_text() instead of check_error() (#552)

Improvements

• Add ASCII validation in set_string() with isascii() (#561)
• Update read_multi.py example (#563)
• Code quality improvements and comprehensive documentation (#568)
• Fix typo: ussage -> usage (#564)

CI/CD & Infrastructure

• Modernize CI/CD: switch to uv, fix Python 3.11+ compatibility (#576)
• Drop Ubuntu 20.04 from CI matrix (#562)

Supported Python versions

• Python 3.10, 3.11, 3.12, 3.13, 3.14

Full Changelog: 2.0.2...2.1.0

2.0.2

What's Changed

• we dont need enum_tools.autoenum by @gijzelaerr in #548

Full Changelog: 2.0.1...2.0.2

2.0.1

What's Changed

• better parsing to avoid bugs when variables name contain whitespaces by @Novecento99 in #529
• update docstring to match new API #537 by @gijzelaerr in #538
• fix indentation of docs by @gijzelaerr in #544
• make test timezone aware by @gijzelaerr in #543

New Contributors

• @Novecento99 made their first contribution in #529

Full Changelog: 2.0.0...2.0.1

2.0.0

major release with backwards compatibility changes

This release is a restructure of the codebase, cleaning up old inconsistencies and spelling mistakes. Although attempts were made to keep the API backwards compatible, a method argument might have changed here and there. This release is also 100% typed, helping us find and fix tiny bugs and mistakes.

This makes the python-snap7 'done', all functionality is implemented and no changes in the API are expected anymore.

Most important changes

• Improve typing by @nikteliy in #516
• Improve use of enum types by @gijzelaerr in #515

Full Changelog: 1.4.1...2.0.0

1.4.1

What's Changed

• update container workflow by @gijzelaerr in #509
• avoid creating compressed tags set by @nikteliy in #510
• Make client and server a contextmanager by @gijzelaerr #512
• Drop Python 3.8 from metadata and doc by @gijzelaerr #513
• Drop Snap7Library singleton and use python functools caching by @gijzelaerr #514
• Doc: Typo and samples for CPU State and CP State @lupaulus #508

Full Changelog: 1.4...1.4.1

1.4

What's Changed

• Fix #431 by @nikteliy in #432
• Add arm32v7 wheel (Issue #376) by @nikteliy in #442
• Update github actions by @nikteliy in #443
• Fix utils by @nikteliy in #444
• Add reusable action by @nikteliy in #446
• append arm in installation doc by @Tathar in #450
• Fix example by @FiloCara in #452
• Fix #451 by @nikteliy in #453
• Add pre-commit by @nikteliy in #460
• add missing lreal to util.py by @spreeker in #487
• Prepare for 1.4 by @gijzelaerr in #477
• Issue 474 fix by @nikteliy in #501
• try to fix more builds by @gijzelaerr in #502
• Also include submodules by @gijzelaerr in #503
• fix build by @nikteliy in #504
• use venv everywhere by @gijzelaerr in #505
• fix bad cli_as_callback implementation by @gijzelaerr in #506
• add python 3.12 wheels, drop 3.8 and older by @gijzelaerr in #474

New Contributors

• @kaisersource made their first contribution in #425
• @Tathar made their first contribution in #450
• @FiloCara made their first contribution in #452

Full Changelog: 1.3...1.4

1.3

What's Changed

• drop python 3.6 versions in checks by @swamper123 in #369
• fix set_string by @swamper123 in #368
• use https for links by @imba-tjd in #370
• use more pythonic syntax by @imba-tjd in #373
• fixed DB class not allowing to write BYTE values to rows by @vmsh0 in #377
• Deprecate old osx by @gijzelaerr in #383
• Add support to read/write space-padded fixed-length strings by @vmsh0 in #378
• DB usability improvements by @vmsh0 in #385
• Make all internal imports relative by @vmsh0 in #386
• fixed typo in portnumber by @Cube707 in #408
• fix linux build by @gijzelaerr in #410
• implement __main__.py enty points by @Cube707 in #409

New Contributors

• @imba-tjd made their first contribution in #370
• @vmsh0 made their first contribution in #377
• @Cube707 made their first contribution in #408

Full Changelog: 1.2...1.3