Access attributes with dot operator with python fhicl module

[knoepfel]

This issue has been migrated from https://cdcvs.fnal.gov/redmine/issues/24091 (FNAL account required)
Originally created by @ikatza on 2020-02-26 10:22:45

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python/fhiclmodule.cc defines a python module to be able to open a fcll file and put the contents on a python dict.

Accessing parameters can become cumbersome:

pset['parameter_table']['parameter_value']

A less cumbersome and more familiar way would be to do:

pset.parameter_table.parameter_value

In Python this is easily achieved by defining __getattr__() function.

What I've done is:

On my python script define:

class dotDict(dict):
    def __getattr__(self,val):
        return self[val]

then feed this class with the python dict:

fcl_params = fhicl.make_pset('file_with_parameters.fcl')
pset = dotDict(fcl_params)
par = pset.parameter_table.parameter_value

Unfortunately I don't understand how to construct this code on the C++ implementation of this module.

Would this be something you would like to add to the module?