Add Python 3 compatibility to PYTHON package

examples/python/funcs.py

@@ -1,9 +1,10 @@
 # Python function that implements a loop of short runs
 # calls back to LAMMPS via "lmp" instance
 # lammps() must be called with ptr=lmpptr for this to work
+from __future__ import print_function
 
 def loop(N,cut0,thresh,lmpptr):
-  print "LOOP ARGS",N,cut0,thresh,lmpptr
+  print("LOOP ARGS",N,cut0,thresh,lmpptr)
   from lammps import lammps
   lmp = lammps(ptr=lmpptr)
   natoms = lmp.get_natoms()
@@ -12,11 +13,12 @@ def loop(N,cut0,thresh,lmpptr):
     cut = cut0 + i*0.1
 
     lmp.set_variable("cut",cut)                 # set a variable in LAMMPS
+
     lmp.command("pair_style lj/cut ${cut}")     # LAMMPS command
     #lmp.command("pair_style lj/cut %d" % cut)  # LAMMPS command option
 
     lmp.command("pair_coeff * * 1.0 1.0")       # ditto
     lmp.command("run 10")                       # ditto
     pe = lmp.extract_compute("thermo_pe",0,0)   # extract total PE from LAMMPS
-    print "PE",pe/natoms,thresh
+    print("PE",pe/natoms,thresh)
     if pe/natoms < thresh: return

examples/python/in.python

@@ -25,13 +25,14 @@ run		10
 # example of catching a syntax error
 
 python          simple here """
+from __future__ import print_function
+
 def simple():
-  import exceptions
-  print "Inside simple function"
+  print("Inside simple function")
   try:
     foo += 1
-  except Exception, e:
-    print "FOO error:",e
+  except Exception as e:
+    print("FOO error:", e)
 """
 
 python          simple invoke