Passing variables to DSF-Python

oozeBot

Can @chrishamm or someone give me a few pointers on how to pass variables to DSF-Python using custom mCodes? I would have assumed it would be like MXXXX V{var.localVar} but DSF-Python reads parameter V as "var.localVar" instead of its value.

Am I missing something simple? Or is there a better way? Thanks

chrishamm

@oozebot You can use the EvaluateExpression command to get the value of expressions. In your case the parameter of MXXXX will have a string value and a property isString which is false meaning that you're dealing with an expression.

I will consider (optional) automatic expression evaluation for the Flush command in v3.5. DSF uses that same mechanism internally, too.

oozeBot

@chrishamm Thanks - but am going to have to plead ignorant and ask for a touch more guidance as I can't find any examples or documentation other than what what auto-generated here: https://duet3d.github.io/DuetSoftwareFramework/api/DuetControlServer.Commands.EvaluateExpression.html

Could you assist by expanding the following snippet on the Python side using EvaluateExpression to read the value of var.localVar? Thanks!

gCode:

var.localVar = "testing"
M1234 V{var.localVar}

Python

cde = intercept_connection.receive_code()
  if cde.type == CodeType.MCode:
    if cde.majorNumber == 1234:
      tVar = ParseParam(cde.parameter("V"))

Falcounet

@oozebot You can use the EvaluateExpression command from DSF in Python in that way :

from dsf.connections import CommandConnection
from dsf.commands.basecommands import evaluate_expression
from dsf.commands.codechannel import CodeChannel

def send_simple_command():
    command_connection = CommandConnection(debug=True)
    command_connection.connect()

    try:
        expression = "{var.localVar}"
        res = command_connection.perform_command(evaluate_expression(CodeChannel.HTTP, expression))
        print(f"Evaluated expression: {res}")
    finally:
        command_connection.close()


if __name__ == "__main__":
    send_simple_command()

You can get the channel you are intercepting the Gcode from using cde.channel instead of CodeChannel.HTTP in the above example.

oozeBot

@falcounet Thank you! This was just the nudge we needed. I was trying to import evaluateexpression, not evaluate_expression - doh!