usingCollections.py

#!/usr/bin/env python3
 
# The VariablesToNtuple (and VariablesToTree) module support collections of variables.
# You specify a collection instead of a variable name, and the collection will be automatically
# resolved to a set of variable names
# the Python module variables.collections defines some default collections, just import it
#
# Thomas Keck and Sam Cunliffe
#
# For full documentation please refer to https://software.belle2.org
# Anything unclear? Ask questions at https://questions.belle2.org
 
import basf2
import variables.collections  # collections of variables
import modularAnalysis as ma  # a shorthand for the analysis tools namespace
from variables import variables as vm  # shorthand name for the VariableManager instance
 
# You can also define collections yourself
vm.addCollection('MyCollection', variables.std_vector('daughter(0, kaonID)', 'daughter(1, pionID)'))
 
mypath = basf2.Path()  # create a new path
 
# add input data and ParticleLoader modules to the path
ma.inputMdstList('default', [basf2.find_file('analysis/tests/mdst.root')], path=mypath)
ma.fillParticleLists([('K-', 'kaonID > 0.2'), ('pi+', 'pionID > 0.2')], path=mypath)
ma.reconstructDecay('D0 -> K- pi+', '1.750 < M < 1.95', path=mypath)
ma.matchMCTruth('D0', path=mypath)
 
# Add the VariablesToNtuple module explicitly
# this will write out one row per candidate in the D0 list
mypath.add_module('VariablesToNtuple',
                  particleList='D0',
                  variables=['kinematics', 'mc_truth', 'MyCollection'],
                  fileName='CollectionVariables.root')
 
# Important note: In order to specify variable collections by string, e.g.
# "kinematics", "mc_truth", etc. you need to import variables.collections, even
# if you do not explicitly use any of its symbols (importing
# variables.collections sets up some default collections).
 
# you might also like to uncomment the following, and read the help for the
# convenient wrapper function:
# print(help(ma.variablesToNtuple))
 
# process the data
basf2.process(mypath)
print(basf2.statistics)