Question

I have a python modules question:

I need to write a script that will take the output from various pieces of hardware and then store them in a database. I know about the current hardware but I do not know about any additional hardware that will be added in the future. Sorry let me be more specific.

The script will retrieve power information from hardware modules connected to power distribution boards. These modules take the raw sensor information and make it available over tcp/ip. I have written functions into the test script that interrogates the hardware modules and gathers the info. The problem is that this will need to be deployed where different hardware modules will be used, not just the ones that I know about. All the hardware modules will make the same info available but they will all do it different ways. Some use telnet or ssh, some provide a web page, some provide and xml output, some will use snmp. I want to create a mechanism that a python module can be written for a new device that pulls out the info and provides it to the script in a standard way so that the script can populate the database and life goes on as normal.

So Instead of adding a new function to the script each time a new hardware module type is encountred and then wrapping it in ‘if’ statements etc… is there a mechanism to offboard that function into a module that can be dynamically added to the script. A plugin type mechanism comes to mind I suppose. But I don’t think that quite fits.

Any suggestions or directions to places where something like this has been used or implemented would be greatly appreciated.

Answer 1

You could use import function in your code. Depending on your Python version, try importlib (Added in Python 2.7) or __import__ function.

You could create plugins for each hardware device you’re going to support. Each such plugin could then register itself somewhere (main module path put in Environment variable or known path in Windows registry). Your code would then check that location (periodically, on startup – depending on your needs) and load each plugin found. You could also use distutils and have plugins packed as egg packages.

Please note that while it works quite well when you’re running from Python sources, it’s getting more complex if you plan to build executables with PyInstaller or Py2exe.