in.fix_python_invoke

# 3d Lennard-Jones melt

units		lj
atom_style	atomic

lattice		fcc 0.8442
region		box block 0 10 0 10 0 10
create_box	1 box
create_atoms	1 box
mass		1 1.0

velocity	all create 3.0 87287

pair_style	lj/cut 2.5
pair_coeff	1 1 1.0 1.0 2.5

neighbor	0.3 bin
neigh_modify	every 20 delay 0 check no

python         end_of_step_callback here """
from __future__ import print_function
from lammps import lammps

def end_of_step_callback(lmp):
  L = lammps(ptr=lmp)
  t = L.extract_global("ntimestep", 0)
  print("### END OF STEP ###", t)

def post_force_callback(lmp, v):
  L = lammps(ptr=lmp)
  t = L.extract_global("ntimestep", 0)
  print("### POST_FORCE ###", t)
"""

fix		1 all nve
fix     2 all python/invoke 50 end_of_step end_of_step_callback
fix     3 all python/invoke 50 post_force post_force_callback

#dump		id all atom 50 dump.melt

#dump		2 all image 25 image.*.jpg type type &
#		axes yes 0.8 0.02 view 60 -30
#dump_modify	2 pad 3

#dump		3 all movie 25 movie.mpg type type &
#		axes yes 0.8 0.02 view 60 -30
#dump_modify	3 pad 3

thermo		50
run		250