DM_append_attribute.py

## @package python.demo.DM_append_attribute
# 
#   example script showing how to append attribute to an existing
#   OPALS datamanager using the Kernel/Processor concept
#   (script works in python 2 and 3)
# 
 
from __future__ import print_function  # print function syntax as in python 3
import sys
 
from opals import pyDM 
 
 
##
# callback object computing an user-defined attribute '_dummy'
class Kernel(pyDM.KernelPoint):
 
    def __init__(self):
        # initialize the base class (mandatory!)
        if sys.version_info >= (3, 0):
            super().__init__()
        else:
            super(Kernel, self).__init__()
        return
 
    def tileFilter(self):
        return None
 
    ##
    # callback notifies about a changed leaf
    def leafChanged(self, leaf):
        print("leafChanged called")
        return
 
    ##
    # callback for processing a point
    def process(self, pt):
        # formula _dummy = Amplitude * EchoWidth
        pt.info().set(0, pt.info().get(1) * pt.info().get(2))
        # return True if the point was changed otherwise False
        # this internally marks the current point leaf as changed (=needs to be written to disk)
        return True
 
 
def DM_append_attribute(filename, maxOutput=1000):
  # pyDM.Datamanager.load parameter: filename(string), readOnly(bool) threadSafety(bool)
  dm = pyDM.Datamanager.load(filename, False, False)
  if not dm:
    print("Unable to open ODM '" + odm + "'")
    sys.exit(1)
 
  # creates the appropriate attribute layout for processing
  lf = pyDM.AddInfoLayoutFactory()
  lf.addColumn(pyDM.ColumnType.float_, "_dummy")  # column 0
  lf.addColumn(pyDM.ColumnSemantic.Amplitude)  # column 1
  lf.addColumn(pyDM.ColumnSemantic.EchoWidth)  # column 2
  layout = lf.getLayout()
 
  print("Ready to append attribute '_dummy' to 'fullwave.odm'")
 
  if sys.version_info >= (3, 0):
    input("Press Enter to continue...")
  else:
    raw_input("Press Enter to continue...")
 
  # create kernel object
  k = Kernel()
  # create processor
  # pyDM.Processor parameter: dm(datamnager), layout, readOnlyView(bool)
  processor = pyDM.Processor(dm, layout, False)
  processor.run(k)  # perform computation
 
  # save manager object
  print("Save manager")
  dm.save()
 
  print("done")
 
if len(sys.argv) == 1:
    print("ODM parameter missing")
    sys.exit(-1)
 
DM_append_attribute(sys.argv[1])