formulaVariablesExample.py

#!/usr/bin/env python3
 
# An example/test of using the formula() metavariable
#
# James Kahn and Sam Cunliffe
#
# For full documentation please refer to https://software.belle2.org
# Anything unclear? Ask questions at https://questions.belle2.org
 
import basf2
from modularAnalysis import inputMdstList
from stdCharged import stdPi
 
mypath = basf2.Path()  # create a path
 
# add input data and ParticleLoader modules to the path
inputMdstList('default', [basf2.find_file('analysis/tests/mdst.root')], path=mypath)
stdPi('95eff', path=mypath)  # grab the standard pions list
 
# you can (and should) make this into something more sensible
nonsense_formula = 'formula(p+nTracks)'
 
# Add the VariablesToNtuple module explicitly
# this will write out one row per candidate in the pi+ list and evaluate
# the nonsense formula for all of them
mypath.add_module(
    'VariablesToNtuple',
    particleList='pi+:95eff',
    variables=['nTracks', 'p', nonsense_formula],
    fileName='formulaTest.root'
)
 
# process the data
basf2.process(mypath)
print(basf2.statistics)