#! /usr/bin/env python

from __future__ import print_function
import numpy
from subprocess import call

#
# build extension from FORTRAN source
#
source = """
       subroutine func_with_callback(callBack, cu, lencu)

       implicit none

       integer :: lencu
       character*8 cu(lencu)
       external callBack

       print *,'Lencu:', lencu

       print *,'Calling callback...'
       call callBack(cu, lencu)
       print *,'Back in fortran...'

       end subroutine func_with_callback
"""

with open("callback.f", "w") as src_file:
    src_file.write(source)

rc = call("f2py callback.f -m callback -h callback.pyf".split())
if rc: quit()

rc = call("f2py -c callback.pyf callback.f".split())
if rc: quit()


#
# define callback function
#
def callBack(cu, lencu):
    print ('In callback:', cu)

#
# call library function with callback
#
from callback import func_with_callback
print(func_with_callback.__doc__)

print("\nNumpy Version:", numpy.__version__, "\n")

cu = numpy.zeros((1, 8), 'c')

func_with_callback(callBack, cu)