Simulation Modeling Sciences
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owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
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Geometry and
Mesh Generation Toolkit
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16. Cubit Scripting with
Python
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Python
• Python is a well established, widely accepted
scripting language. Its use within the
engineering community continues to grow.
– Abaqus
– Paraview
– PyTrilinos
• Some useful links to learn Python
– Official website: www.python.org
– Getting started: www.python.org/about/gettingstarted/
– Tutorial (2.7): docs.python.org/2/tutorial/index.html
– Reference (2.7): docs.python.org/2/reference/index.html
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Enabling the Script Tab from Cubit
• Select Tools – Options
– Layout
• Select “Show Script
Tab”
• The script tab will
allow direct entry of
python commands.
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Python Journal Editor
Access from menu
Access from toolbar
Journal Editor with Cubit commands Journal Editor with Python commands
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Custom Toolbars
Access editor from
menu
Access editor from
toolbar
Example custom toolbar
• Execute a series of
Python commands at
the click of a button
• Execute a Python
script
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Custom Toolbars
Include “#!python” to tell Cubit to
interpret the commands as Python
(necessary for this tool only)
Create a custom tool button and
write Python commands in place,
just like Cubit commands.
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Custom Toolbars
Create a Python script
button and choose a Python
script to run.
Select the Python script to
run.
(Optional) choose a directory
from which to run the script.
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Cubit Interface
• Primarily, a query interface into Cubit
– double mesh_size =
cubit.get_mesh_size(“volume”, 22);
• Accessible via C++ or python
• Change state by using cubit.cmd(“ ... “)
– import cubit
– cubit.cmd(“create brick x 10 y 10 z 10”)
– cubit.cmd(“mesh volume 1,3,5”)
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Example 1
• Open ngon.py with the journal editor
• Play the script
• Change the parameters
• Play again
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Example 2
• Create a python script to compute and print the
minimum shape metric for all volumes. Consider
using the following CubitInterface functions
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get_entities()
get_volume_hexes()
get_quality_value()
In the Cubit Journal File (Python) Editor
Simulation Modeling Sciences
Example 2
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all_vols = cubit.get_entities("volume")
min_quality = 1.0
for vol in all_vols:
vhexes = cubit.get_volume_hexes(vol)
for hex in vhexes:
q = cubit.get_quality_value("hex", hex, "shape")
if q < min_quality:
min_quality = q
print 'min quality = ', min_quality
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Cubit Extended Interface
• Create “pythonic” objects in Cubit
• Reduce (but not eliminate) id issues
bri = cubit.brick(10,5,3)
cyl = cubit.cylinder(12,2,2,2)
vols = cubit.subtract([cyl], [bri])
v = vols[0].volumes()
v[0].mesh()
print dir(v[0])
print v[0].id()
v[0].mesh()
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Python Help
• Documentation
– Help Manual online or built-in Appendix/Python
• Python prompt
– print dir(object)
Help
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Black Box Cubit
• Cubit can also be run from inside python
– Set your environment variable PATH to include
the installed Cubit libraries
– You may also need to set PYTHONPATH to the
same place
Run Python
import cubit
cubit.init([“”])
cubit.cmd(“brick x 10”)
• This allows you to run Cubit programatically and
interact with other tools.
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Example 3
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• Copy your script from Example 2 to a text editor
• Add the ability to import a mesh
• Make the script you created above run on the
hexes in the mesh and print the result
In the native operating system using python 2.7
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Example 3
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#!python
import sys
# add Cubit libraries to your path
sys.path.append('/Applications/Cubit-15.4/Cubit.app/Contents/MacOS')
import cubit
cubit.init(['cubit','-nojournal'])
cubit.cmd('import mesh geom "mesh.g"')
all_vols = cubit.get_entities("volume")
min_quality = 1.0
for vol in all_vols:
vhexes = cubit.get_volume_hexes(vol)
for hex in vhexes:
q = cubit.get_quality_value("hex", hex, "shape")
if q < min_quality:
min_quality = q
print 'min quality = ', min_quality
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Customization
• Cubit can support some additions to the GUI
– Add new menu items
– Add new dialogs
– Cannot currently add new control panels
• Use PyQt5 - a python interface to Qt
from PyQt5 import QtGui
QtGui.QMessageBox.question(None, “Title”, “Hello”)
