Expression¶

Type:	string
Range:	[]
Default:	-/-
Appearance:	simple
Excludes:	Function, Module

This parameter is used to define a tensor field of type “force surface-density” by means of a Python expression within the .jcm input file. The syntax is the following:

ForceSurfaceDensity {
  Python {
     Expression = " ... # your python scripting
                    ...
                    value = ... # set return value

                   "

     # define one or more parameters
     Parameter {
       Name = "Para1"
       ...
     }
     Parameter {
       Name = "Para2"
       ...

     }
  }
}

The string value Expression has to be valid Python code and is interpreted in the following way:

The NumPy-package is automatically imported when evaluating the expression.
Any parameter as defined by a Parameter section is available within the Python expression as an NumPy object named accordingly to the value of the parameter Name.
The position $\pvec{x}$ and the time $t$ are available as NumPy objects name X and t respectively.
For time-harmonic electromagnetic problems the angular frequency $\omega$ can be addressed by EMOmega, (EM stands for electromagnetic).
The expression must define a NumPy object named value which contains the return value of appropriate shape (force surface-density is a 3-vector).
Keep in mind the Python indentation rule.

For practical examples we refer to the following cases: