1. CMSSW Configuration Using python Rick Wilkinson

2. Python configurations u Your cfg, cfi, and cffs will not be supported in CMSSW_2_1_0. u They’ll be replaced by python equivalents u Most of the cfis and cffs have been translated, committed, and published to CMSSW_2_1_X è My “day job”

3. Why python? Nice, readable syntax Easy to learn Popular Interfaces easily to C++ Through boost::python

4. Why change? Job configurations are getting big and complex Need to easily edit configurations, both by users and by scripts in GRID jobs In old system, every “replace” functionality had to be coded by hand Some still missing, such as random access to vectors We’ve already had to write two systems to convert configurations to python and back.

5. How different is the syntax? Not very different. It’s based on the old system process DIGI = { process DIGI = { hcalDigis = HcalDigiProducer { hcalDigis = HcalDigiProducer { bool doNoise = true bool doNoise = true } replace hcalDigis.doNoise = false replace hcalDigis.doNoise = false import FWCore.ParameterSet.Config as cms process = cms.Process(“DIGI”) process.hcalDigis = cms.EDProducer(“HcalDigiProducer”, doNoise = cms.bool(True) doNoise = cms.bool(True) ) process.hcalDigis.doNoise = False

6. Sample The process is the basic object representing the configuration. import FWCore.ParameterSet.Config as cms process = cms.Process(“SIM”) # Input source process.source = cms.Source("PoolSource", fileNames = cms.untracked.vstring('file:gen.root') fileNames = cms.untracked.vstring('file:gen.root')) # Modules process.load(“Configuration.StandardSequences.VtxSmearedGauss_cff”) process.load(“SimG4Core.Application.g4SimHits_cfi”) process.g4SimHits.UseMagneticField = False # Output process.load(“Configuration.EventContent.EventContent_cff”) process.FEVT = cms.OutputModule("PoolOutputModule", process.FEVTSIMEventContent, process.FEVTSIMEventContent, fileName = cms.untracked.string('sim.root') fileName = cms.untracked.string('sim.root')) # Execution paths process.p1 = cms.Path(process.VtxSmeared+process.g4SimHits)

7. Translation Tools Tools exists that will translate your file, and automatically translate any files you include. > python FWCore/ParameterSet/python/cfg2py.py your.cfg dumps python-language output dumps python-language output > python FWCore/ParameterSet/python/translate.py Sub/Package/data/your.cff creates a file, Sub/Package/python/your_cff.py, overwriting what was there. > python FWCore/ParameterSet/python/comments.py Sub/Package/data/your.cff transfers the comments in your cff to the appropriate cff.py

8. Other Documentation Wiki page: https://twiki.cern.ch/twiki/bin/view/CMS/SWGuideAboutPythonConfigFile Benedikt’s Tutorial: http://indico.cern.ch/conferenceDisplay.py?confId=28445