setDescriptorTemplate()

if 'setDescriptorTemplate' not in dir(DecayTreeTuple):
  print "Adding setDescriptorTemplate() to DecayTreeTuple because this DaVinci is too old"
  # Bored of typing decay descriptors and adding carat symbols?
  # Use some python string template magic to set your decay descriptor
  # and define your branches all in one go without excess typing!
  def setDescriptorTemplate(self, template):
    if 'Decay' not in dir(self):
      raise TypeError, ("You're trying to set the decay descriptor of something that doesn't have one, " + str(type(self)))
    if 'Branches' not in dir(self):
      raise TypeError, ("You're trying to define branches on something that doesn't support them, " + str(type(self)))

    from string import Template
    # The argument 'template' is a Python string template
    # e.g. "${D}[D0 -> ${kaon}K- ${pion}pi+]CC"
    # Here ["D", "kaon", "pion"] are the branch names you want
    dd = Template(template)

    # This parses the temlate to get the list of branch names,
    # i.e. ["D", "kaon", "pion"]
    particles = [y[1] if len(y[1]) else y[2] for y in dd.pattern.findall(dd.template) if len(y[1]) or len(y[2])]

    # To form the decay descriptor, we need to mark all the particles
    # except for the top-level particle, which is included by default
    mapping = { p : '^' for p in particles }
    mapping[particles[0]] = ''

    # Make the descriptor
    # "[D0 -> ^K- ^pi+]CC"
    self.Decay = dd.substitute(mapping)

    # Now make the branches
    branches = { }
    for p in particles:
      # Need a version of the descriptor where particle 'p' is marked but nothing else is.
      mapping = { q : '^' if p == q else '' for q in particles }
      branches[p] = dd.substitute(mapping)

    # Finally, add the branches to the DecayTreeTuple
    return self.addBranches(branches)
  DecayTreeTuple.setDescriptorTemplate = setDescriptorTemplate