Python is a popular scripting language with an interactive interpreter. Geant4Py, a Geant4-Python bridge, provides a bridge for Geant4 classes. This enables to directly access Geant4 classes from Python scripting. User applications can be easily configured with many Python third-party modules, such as PyROOT, on the Python software bus.
Geant4Py is supplied in the directory environments/g4py/
of the Geant4 source package.
Geant4Py requires the Boost-C++ external library, which helps Python binding of C++ codes.
Building system is completely migrated to CMake system. Before building library, GEANT4_INSTALL environment variable should be set to the path specified by "CMAKE_INSTALL_PREFIX" when building Geant4.
# export GEANT4_INSTALL="Geant4 install path" (zsh, bash) # setenv GEANT4_INSTALL "Geant4 install path" (csh)
Then
# mkdir build # cd build # cmake .. # make # make install
If you want to run the testing component,
# cd build/tests # make; make install
By default, Geant4Py is installed in "g4py"/lib(64) directory.
PYTHONPATH environment variable
should be set at tun time.
PYTHONPATH environment variable indicates
Python module search directories, given by a colon-separated list
of directories. Practically, the variable is
(your g4py directory)/lib:(your g4py directory)/lib/examples:(your g4py directory)/lib/tests
.
To use Geant4Py, you start with importing the module called "Geant4".
# python Python 2.7.5 (default, Mar 9 2014, 22:15:05) [GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> from Geant4 import * ************************************************************* Geant4 version Name: geant4-10-01 (5-December-2014) Copyright : Geant4 Collaboration Reference : NIM A 506 (2003), 250-303 WWW : http://cern.ch/geant4 ************************************************************* Visualization Manager instantiating... >>>
When importing the Geant4 module, the G4RunManager
object will be automatically instantiated. Geant4 singleton objects are also
automatically instantiated. These singleton objects can be accessed
by "gXXXX" variables, like "gRunManager".
gLossTableManager gTerminate gApplyUICommand gMaterialTable gTrackingManager gControlExecute gNistManager gTransportationManager gElementTable gParticleIterator gUImanager gEmCalculator gParticleTable gVisManager gEventManager gProcessTable gExceptionHandler gProductionCutsTable gG4Date gRunManager gG4VERSION_NUMBER gRunManagerKernel gG4Version gStackManager gGeometryManager gStartUISession gGetCurrentValues gStateManager
Once a Python object of a Geant4 class instantiated, Geant4 methods can be directly called the same way as in C++.
>>> from Geant4 import * ************************************************************* Geant4 version Name: geant4-10-01 (5-December-2014) Copyright : Geant4 Collaboration Reference : NIM A 506 (2003), 250-303 WWW : http://cern.ch/geant4 ************************************************************* Visualization Manager instantiating... >>> print gRunManager.GetVersionString() Geant4 version Name: geant4-10-01 (5-December-2014)
Geant4Py provides additional utility modules called "g4py" in the directory
site-modules
. It consists of predifined geometries,
materials, physics lists, primary generator actions, and so on.
The ezgeom module provides an alternative way of defining simple geometry. An example code for defining a simple geometry is shown here:
import g4py.ezgeom from g4py.ezgeom import G4EzVolume def ConstructGeom(): print "* Constructing geometry..." # reset world material air= G4Material.GetMaterial("G4_AIR") g4py.ezgeom.SetWorldMaterial(air) # a target box is placed global target target= G4EzVolume("Target") au= G4Material.GetMaterial("G4_Au") target.CreateTubeVolume(au, 0., 1.*cm, 1.*mm) target.PlaceIt(G4ThreeVector(0.,0.,-10.*cm))
The NISTmaterials module provides an instant use of Geant4 NIST materials. An example code for creating NIST materials:
from Geant4 import * import g4py.NISTmaterials g4py.NISTmaterials.Construct() print Geant4.gMaterialTable
The ParticleGun module provides
a primary generator action with G4ParticleGun
.
An example code is shown here:
import g4py.ParticleGun # normal way for constructing user primary generator action #pgPGA= g4py.ParticleGun.ParticleGunAction() #gRunManager.SetUserAction(pgPGA) #pg= pgPGA.GetParticleGun() # 2nd way, short-cut way pg= g4py.ParticleGun.Construct() # set parameters of particle gun pg.SetParticleByName("e-") pg.SetParticleEnergy(300.*MeV) primary_position= G4ThreeVector(0.,0., -14.9*cm) primary_direction= G4ThreeVector(0.2, 0., 1.) pg.SetParticlePosition(primary_position) pg.SetParticleMomentumDirection(primary_direction)
There are some examples of Geant4Py in the directories
"tests/"
and "examples/"
.
"tests/"
directory,
gtest01 : exposes a user application gtest02 : test for using site-module packages gtest03 : test for ezgeom package gtest04 : test for getting command tree and command information gtest05 : test for constructing CSG geometries in Python gtest06 : test for constructing/visualizing boolean geoemtries gtest07 : test for checking overlapped geometries
"examples/"
directory contains
a set of examples of Geant4Py.
An example of "water phantom dosimetry". This demo program shows that a Geant4 application well coworks with Root on Python front end. VisManager, PrimaryGeneratorAction, UserAction-s, histogramming with Root are implemented in Python;
Educational examples with Graphical User Interface using
TKinter
* lesson1
The first version of the courseware of the mass attenuation coefficient.
* lesson2
GUI interface of ExN03, which can control geometry configuration, intial particle condition, physics processes, cut value, magnetic field and visualization outputs.
Examples of plotting photon cross sections and stopping powers with Root.
Examples of writing/reading user's geometry to/from a GDML file