Hi,

You must define a field type function in res.partner. and in this function get information in another object.

def _get_other(self,cr,uid,ids,field,arg,context=None):       
       res={}
       //your treatment
       return res

_columns = {
          'other': fields.function(_get_other, method=True, type='float',string='Info other'),
          }

Thank You.