make python functions examples more complete by adding exception handling and...

  lmp = lammps(ptr=lmpptr)

  natoms = lmp.get_natoms()

  try:

    for i in range(N):

      cut = cut0 + i*0.1

      pe = lmp.extract_compute("thermo_pe",0,0)   # extract total PE from LAMMPS

      print("PE",pe/natoms,thresh)

      if pe/natoms < thresh: return

  except Exception as e:

    print("LOOP error:", e)

from __future__ import print_function

def simple():

  foo = 0

  print("Inside simple function")

  try:

    foo += 1