Generating a Q object for ensuring maximal depth for onetoones.

qobj.py

LOOKUP_SEP = '__'  # fake it.

def Q(**kws):  # fake it.
  return kws

def make(relation_str, sep=LOOKUP_SEP):
  """
  Given something like:
    'a__b__c__d__e'
  return a Q object composed of:
    {
      'a__isnull': False, 
      'a__b__isnull': False, 
      'a__b__c__isnull': False, 
      'a__b__c__d__isnull': False, 
      'a__b__c__d__e__isnull': False
    }
  all AND'd together.
  """
  template = '{val!s}__isnull'
  if LOOKUP_SEP not in relation_str:
    to_q = {template.format(val=relation_str): False}
  else:
    relations = relation_str.split(LOOKUP_SEP)
    relations_count = len(relations)
    
    def sliceup(iterable, length):
      return LOOKUP_SEP.join(iterable[0:length+1])
      
    to_q = {
      template.format(val=sliceup(relations, x)): False 
      for x in range(relations_count)
    }
  return Q(**to_q)