Modifying moose input files

In this example we will use mooseherder’s input modifier to programmatically change variables in a moose .i input script.

We start by importing the packages we need for this example.

from pathlib import Path

# Pyvale imports
import pyvale.dataset as dataset
from pyvale.mooseherder import InputModifier

We use the input file for a simple thermo-mechanical cube with higher order quads. We pass this to our input modifier specifying the moose comment character(s) as ‘#’ and moose input files do not have a line end character so we pass an empty string. In the next example we will modify a gmsh script where we will need to specify a line ending character.

moose_input = dataset.element_case_input_path(dataset.EElemTest.HEX20)
moose_mod = InputModifier(moose_input, comment_chars="#", end_chars="")

Note that the input modifier class only looks for variables between specified sentinel characters in comment lines which starts with ‘_*’ and ends with ‘**’ . An example of what variable block can be found in the moose input file.

We then print the variables found in the moose input file to the console which are returned to us as a dictionary keyed by the variables string name in the file:

print(moose_mod.get_vars())
print()

We can update variables using the input modifier, we just need to create a dictionary keyed by the variable name we want to change and the value we want the variable to take. If the variable does not exist in the input file then an error will be raised. Here we will change the number of elements in ‘x’ and the elastic modulus.

new_vars = {"nElemX": 4, "EMod": 3.3e9}
moose_mod.update_vars(new_vars)

Let’s check that the variables in the dictionary have been updated to match what we have changed:

print(moose_mod.get_vars())
print()

Now we want to save the modified input file so we first create the standard pyvale-output directory if it does not exist. Then we write the file to that directory with suitable file name. Have a look at the file in the pyvale-output directory to verify the variables have been changed.

output_path = Path.cwd() / "pyvale-output"
if not output_path.is_dir():
    output_path.mkdir(parents=True, exist_ok=True)

moose_save = output_path/"moose-mod-vars.i"
moose_mod.write_file(moose_save)