Override create method by inheritance

Yes it's possible to override create method, why it's calling your create function twice will depend on more factors than you are currently sharing, please include a link if possible to a minimized problem case using http://gist.github.com or similar pasting services.

here, you have my code :

class project_work(osv.osv):

  def create(self, cr, uid, vals, *args, **kwargs):
        obj_timesheet = self.pool.get('hr.analytic.timesheet')
        project_obj = self.pool.get('project.project')
        task_obj = self.pool.get('project.task')
        uom_obj = self.pool.get('product.uom')

        vals_line = {}
        context = kwargs.get('context', {})
        if not context.get('no_analytic_entry',False):
            obj_task = task_obj.browse(cr, uid, vals['task_id'])
            result = self.get_user_related_details(cr, uid, vals.get('user_id', uid))
            vals_line['name'] = '%s: %s' % (tools.ustr(obj_task.name), tools.ustr(vals['name']) or '/')
            vals_line['user_id'] = vals['user_id']
            vals_line['product_id'] = vals['product_id']
            vals_line['date'] = vals['date'][:10]
            vals_line['to_invoice'] = vals['to_invoice']

            #calculate quantity based on employee's product's uom
            vals_line['unit_amount'] = vals['hours']

            default_uom = self.pool.get('res.users').browse(cr, uid, uid).company_id.project_time_mode_id.id
            if result['product_uom_id'] != default_uom:
                vals_line['unit_amount'] = uom_obj._compute_qty(cr, uid, default_uom, vals['hours'], result['product_uom_id'])
            acc_id = obj_task.project_id and obj_task.project_id.analytic_account_id.id or False
            if acc_id:
                vals_line['account_id'] = acc_id
                res = obj_timesheet.on_change_account_id(cr, uid, False, acc_id)
                if res.get('value'):
                    vals_line.update(res['value'])
                vals_line['general_account_id'] = result['general_account_id']
                vals_line['journal_id'] = result['journal_id']
                vals_line['amount'] = 0.0
                vals_line['product_uom_id'] = result['product_uom_id']
                amount = vals_line['unit_amount']
                prod_id = vals_line['product_id']
                unit = False
                timeline_id = obj_timesheet.create(cr, uid, vals=vals_line, context=context)

                # Compute based on pricetype
                amount_unit = obj_timesheet.on_change_unit_amount(cr, uid, timeline_id,
                    prod_id, amount, False, vals['hours'], vals_line['journal_id'],vals['to_invoice'], context=context)
                if amount_unit and 'amount' in amount_unit.get('value',{}):
                    updv = { 'amount': amount_unit['value']['amount'],'billable_amount': amount_unit['value']['billable_amount'] }
                    obj_timesheet.write(cr, uid, [timeline_id], updv, context=context)
                vals['hr_analytic_timesheet_id'] = timeline_id
                vals['billable_amount'] = amount_unit['value']['billable_amount']
        return super(project_work,self).create(cr, uid, vals, *args, **kwargs)

project_work()

Thanks , I solved the issue.

I solved the issue

Thanks Serpent Consulting Services, that solved my question.