how to get from the ODOO screen itself

Hi,

You can do as following:

    def _get_currency(self, cr, uid, context=None):
        user_obj = self.pool.get('res.users')
        currency_obj = self.pool.get('res.currency')
        user = user_obj.browse(cr, uid, uid, context=context)

        if user.company_id:
            return user.company_id.currency_id.id
        else:
            return currency_obj.search(cr, uid, [('rate', '=', 1.0)])[0]
_defaults = {      
        'currency': _get_currency,
 }

self.env.company.currency_id