Skip to main content

No project description provided

Project description

Pycomm Scanlist

Python module for managing a list of tags being read from a Rockwell Automation PLC.

Scanlist Class

The module implements a Scanlist class with a required parameter of IP Address. Optionally, a plc_type and a change_handler parameter can be passed to the class.

plc_type parameter

Due to different implementations within pycomm for Micro800 PLCs, in order to read from a Micro800 PLC, the value of plc_type must be "Micro800". The default value for plc_type is "CLX" for ControlLogix/CompactLogix PLCs.

change_handler parameter

The change_handler should be a function with a required parameter sender and an optional parameter eargs. sender is a reference to the instance of Tag that has changed.

The default implementation of change_handler is:

def change_handler(sender):
    """Handle a tag value change."""
    print("{} changed from {} to {}".format(sender.tag_name, sender.last_value, sender.value))

Scanlist.add(tag_name) function

Scanlist.add takes one parameter tag_name and adds it to the list of tags to scan.

Scanlist.remove(tag_name) function

Scanlist.add takes one parameter tag_name and removes it from the list of tags to scan.

Scanlist.print_tag_names() function

Scanlist.print_tag_names() prints all tag names currently in the list of tags to scan.

Scanlist.scan() function

Scanlist.scan() polls all tags in the list of tags to scan and runs the change_handler function if the tag value has changed.


The following example creates two scanlists, one for the Micro800 PLC at and another for the CLX PLC at Each PLC has 4 tags in the scanlist.

import time
from pycomm_scanlist import Scanlist

def handle_tag_change(sender, eargs=None):
    """Handle a tag value change."""
    print("{} CHANGED FROM {} TO {}".format(sender.tag_name, sender.last_value, sender.value))

micro_scan_list = Scanlist("", plc_type="Micro800", change_handler=handle_tag_change)

clx_scan_list = Scanlist("", change_handler=handle_tag_change)


while True:


  • Add tests to increase coverage.
  • Per-tag handlers?
  • PyPi package


Project details

Release history Release notifications

This version


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for pycomm-scanlist, version 0.1
Filename, size File type Python version Upload date Hashes
Filename, size pycomm_scanlist-0.1-py2-none-any.whl (4.9 kB) File type Wheel Python version py2 Upload date Hashes View hashes
Filename, size pycomm-scanlist-0.1.tar.gz (3.8 kB) File type Source Python version None Upload date Hashes View hashes

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page