Tips and Tricks

Here’s a random collection of some tips and tricks that should make your life easier.

Note

All examples come from one of the MontePy test inputs. You can access it by:

import montepy
problem = montepy.read_input("tests/inputs/test.imcnp")
surfaces = problem.surfaces

Getting The Highest Plane

With the montepy.surface_collection.Surfaces mnemonic generators you can quickly get the “extreme” surfaces, using the max and min function.

By default though these functions will sort the surfaces by surface number. Rather you need to use the key argument to change how the surfaces are sorted. These examples use python lambda expressions, which are very short anonymous functions.

Here are some examples:

Getting Highest PZ plane

>>> max(surfaces.pz, key = lambda x: x.location)
SURFACE: 1025, PZ, periodic surface: None, transform: None, constants: [15.0]

Getting the Lowest PZ plane

Similarly you can get the lowest surface with the min function:

>>> min(surfaces.pz, key = lambda x: x.location)
SURFACE: 1020, PZ, periodic surface: None, transform: None, constants: [10.0]

Getting the Largest CZ Cylinder

Similar to before you can use this method to find cylinders by their radius:

>>> max(surfaces.cz, key = lambda x: x.radius)
SURFACE: 1015, CZ, periodic surface: None, transform: None, constants: [5.0]

Translating Cells

Translating experiment axially

For some problems you can quickly move a whole problem axially (in z) with a simple loop like:

for surface in problem.surfaces.pz:
    surface.location += 10

Note

This only works for problems that are infinite in Z, with “cutting” PZ planes, such as a fuel rod. This is because only the PZ surfaces are moving. If you had a sphere in the problem for instance, this would break the problem geometry then as the sphere would not move as well.

Note

Make sure you loop over all the surfaces in the problem, and not over all the cells. For instance:

import montepy
problem = montepy.MCNP_Problem("foo.imcnp")
for cell in problem.cells:
    for surface in cell.surfaces:
        surface.location += 10

will cause geometry errors. Surfaces are commonly used by multiple cells so each surface may be translated repeatedly.