| 7. Python Interface | ||
|---|---|---|
 | Appendix . Appendices |  |
| 7. Python Interface | ||
|---|---|---|
| | Appendix . Appendices | |
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.
Geant4Py provides a configure script for building modules.
`configure' configures Geant4Py to adapt to many kinds of systems.
Usage: ./configure SYSTEM [OPTION]... [VAR=VALUE]...
SYSTEM: System type (see Supported Arhitectures)
Options:
-h, --help Display this help and exit
Installation directories:
--prefix=PREFIX Installation prefix [./]
--libdir=DIR Python modules dir [PREFIX/lib]
Fine tuning of the library path:
--with-g4install-dir=DIR Geant4 installed dir
--with-python-incdir=DIR Python header dir [/usr/include/python(2.#)],
(location of pyconfig.h)
--with-python-libdir=DIR Python library dir [/usr/lib(64)]
--with-python3 Use Python3
--with-boost-incdir=DIR BOOST-C++ header dir [/usr/include],
(location of boost/)
--with-boost-libdir=DIR BOOST-C++ library dir [/usr/lib]
--with-boost-python-lib=LIB library name of libboost_python.so [boost_python]
--with-extra-dir=DIR Install path for extra packages [/usr/local]
--with-xercesc-incdir=DIR Xerces-C header dir [/usr/include]
--with-xercesc-libdir=DIR Xerces-C library dir [/usr/lib(64)]
Enable/disable options: prefix with either --enable- or --disable-
openglx OpenGLX support [auto]
openglxm OpenGLXm support [disable]
raytracerx RayTracerX support [disable]
Supported Architectures:
linux for Linux gcc (32bit)
linux64 for Linux gcc (64bit)
linuxx8664gcc for Linux gcc (64bit)
macosx for Apple OS X with gcc
For example, you run it like
# ./configure linux64 -with-g4install-dir=[geant4 install path with CMake]
The configure script automatically check your environment,
and create config/config.gmk,
which describes your envrionment.
After executing the configure script successfully, then
# make # make install
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.
To use Geant4Py, you start with importing the module called "Geant4".
# python
Python 2.6.2 (r262:71600, Oct 24 2009, 03:15:21)
[GCC 4.4.1 [gcc-4_4-branch revision 150839]] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from Geant4 import *
*************************************************************
Geant4 version Name: geant4-09-03 (18-December-2009)
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: geant4-09-03 (18-December-2009)
Copyright : Geant4 Collaboration
Reference : NIM A 506 (2003), 250-303
WWW : http://cern.ch/geant4
*************************************************************
Visualization Manager instantiating...
>>> print gRunManager.GetVersionString()
Geant4 version Name: geant4-09-03 (18-December-2009)
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
| |  | |
| 6. Development and Debug Tools |  | 8. Geant4 Material Database |