pycomm3 - A Python Ethernet/IP library for communicating with Allen-Bradley PLCs.#

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pycomm3 started as a Python 3 fork of pycomm, which is a Python 2 library for communicating with Allen-Bradley PLCs using Ethernet/IP. The initial Python 3 port was done in this fork and was used as the base for pycomm3. Since then, the library has been almost entirely rewritten and the API is no longer compatible with pycomm. Without the hard work done by the original pycomm developers, pycomm3 would not exist. This library seeks to expand upon their great work.


pycomm3 includes 3 drivers:

  • CIPDriver

    This driver is the base driver for the library, it handles common CIP services used by the other drivers. Things like opening/closing a connection, register/unregister sessions, forward open/close services, device discovery, and generic messaging. It can be used to connect to any Ethernet/IP device, like: drives, switches, meters, and other non-PLC devices.

  • LogixDriver

    This driver supports services specific to ControlLogix, CompactLogix, and Micro800 PLCs. Services like reading/writing tags, uploading the tag list, and getting/setting the PLC time.

  • SLCDriver

    This driver supports basic reading/writing data files in a SLC500 or MicroLogix PLCs. It is a port of the SlcDriver from pycomm with minimal changes to make the API similar to the other drivers. Currently this driver is considered legacy and it’s development will be on a limited basis.


PLCs can be used to control heavy or dangerous equipment, this library is provided “as is” and makes no guarantees on its reliability in a production environment. This library makes no promises in the completeness or correctness of the protocol implementations and should not be solely relied upon for critical systems. The development for this library is aimed at providing quick and convenient access for reading/writing data inside Allen-Bradley PLCs.


The package can be installed from PyPI using pip: pip install pycomm3 or python -m pip install pycomm3.

Optionally, you may configure logging using the Python standard logging library. A convenience method is provided to help configure basic logging, see the Logging Section in the docs for more information.

Python and OS Support#

pycomm3 is a Python 3-only library and is supported on Python versions from 3.6.1 up to 3.10. There should be no OS-specific requirements and should be able to run on any OS that Python is supported on. Development and testing is done primarily on Windows 10. If you encounter an OS-related problem, please open an issue in the GitHub repository and it will be investigated.


Python 3.6.0 is not supported due to NamedTuple not supporting default values and methods until 3.6.1