SectionList iteration no longer changes CAS.

[nrnhines]

See neuronsimulator/nrn#596
Closes #5

See also neuronsimulator/nrn#1831

[nrnhines]

Though not quite relevant to this PR (because not related to NEURON + PYTHON API change) I would also suggest carefully reviewing any idiom use like:

stimulusClass.py:        stim = h.IClamp(0, axon.allseclist)

as the second arg is ignored and should probably be written

stim = h.IClamp(0, sec=axon.allseclist) # but still wrong as  allseclist seems to be a NEURON SectionList

The best syntax for POINT_PROCESS construction (and many other methods that need a currently accessed section and a location on that section) is to use the nrn.Segment idiom

stim = h.IClamp(axon.allseclist[0](0)) # assumes allseclist is just a normal Python list of nrn.Section:  for sec in allseclist: still works the same way. Of course if you are using h.SectionList methods not available  to Python list...

[chlubba]

Thank you very much for your contribution to PyPNS, @nrnhines. Merged.

[nrnhines]

Just curious. Is there a simple setting so that python test.py produces deterministic results to allow comparison between runs with different versions of Python and NEURON. I often use Random123 so that I can validate threads and MPI runs as well.
https://nrn.readthedocs.io/en/latest/python/programming/math/random.html?highlight=random123#Random.Random123

[chlubba]

I cannot test this right now and make sure. But the only source of variability in the output of python test.py should be the tortuosity of the axon. Setting the random direction component to 0.0 instead of 0.2 would then make the output deterministic.

line 22:
rdc = 0.0 # random direction component