Using pNbody with scripts
****************************


In addition to using **pNbody** in the python interpreter, 
it is very useful to use **pNbody** in python scripts. Usually a python script 
begin by the line #!/usr/bin/env python and must be executable::

  chmod a+x file.py 
  
The following example (slice.py), we show how to write a script that opens a gadget file, 
select gas particles and cut a thin slice 

.. math:: -1000<y<1000

The new files are saved using the extension .slice. ::
 
  #!/usr/bin/env python3
  
  import sys
  from pNbody import *
  
  files = sys.argv[1:]
  
  for file in files:
    print("slicing",file)
    nb = Nbody(file,ftype='gadget')
    nb = nb.select('gas')
    nb = nb.selectc((np.fabs(nb.pos[:,1])<1000))
    nb.rename(file+'.slice')
    nb.write()
  
 
In your ``pnbody_example`` directory, you can run this script with the command::

  ./scripts/slice.py gadget_z*0.dat

or::

  python ./scripts/slice.py gadget_z*0.dat