I have been trying different debugging methods but everything fails.How can i print a variable or msg in log.

i am using tail -f /var/log/openerp/openerp-server.log& for log

my code is 
import logging
from openerp.osv import fields, osv
import time
print "a"*1000

_logger = logging.getLogger(__name__)
class calldata_print_report_wiz(osv.osv_memory):
    _name = "calldata.print.report.wiz"

    def _sel_func(self, cr, uid,context=None):

     print "hello"*100
     obj = self.pool.get('calldata1')
     ids = obj.search(cr, uid, [])
     res = obj.read(cr, uid, ids, ['Caller'], context)
     _logger.debug('Create a %s with vals %s', self._name, res)
     res =[r['Caller'] for r in res]
     return res

    _columns = {
        'date_start': fields.date('Date Start', required=True),
        'date_end': fields.date('Date End', required=True),
#        'Callers':fields.many2one(
 #       'calldata1',

  #   'Callers',
   #     selection=_sel_func
    #    )
       'caller_id':fields.selection(_sel_func, string='Caller'),
   }
    _defaults = {
        'date_start': lambda *a: time.strftime('%Y-%m-%d'),
        'date_end': lambda *a: time.strftime('%Y-%m-%d'),


     }

    def print_report(self, cr, uid, ids, context=None):
      import pdb
      pdb.set_trace()
       import netsvc
       netsvc.Logger().notifyChannel('calldetails1', netsvc.LOG_DEBUG, "Hello")

      if context is None:
            context = {}

      datas = {'ids': context.get('active_ids', [])}
      res = self.read(cr, uid, ids, ['date_start', 'date_end', 'Caller_id'], context=context)
      res = res and res[0] or {}
      datas['form'] = res
      return {
            'type': 'ir.actions.report.xml',
            'report_name':'call',
           }
calldata_print_report_wiz()

Any one please help?