In below example, I have written Python script to remove 'provision' from selection list when configuring Cash Flow Codes. Paste below python code in .py file :

def fields_get(self, cr, uid, fields=None, context=None): 
 res = super(account_cashflow_code, self).fields_get(cr, uid, fields, context) 
if context.get('manage_cfc') and res.get('type'): 
            res['type']['selection'].remove(('provision', u'Provision')) 
        # rename date fields 
        format_date = self.format_date 
        if context.has_key('date_start'): 
            date_start = datetime.strptime(context.get('date_start'), '%Y-%m-%d').date()            
            nbr_days = int(context.get('nbr_days')) 
            days = [format_date(cr, uid, date_start, context)] + [format_date(cr, uid, date_start + timedelta(days=x), context) for x in range(1, nbr_days)]        
            for x in range(1, nbr_days + 1): 
                if x < 10: 
                    field = 'balance_day0' + str(x) 
                else: 
                    field = 'balance_day' + str(x) 
                if res.get(field, None): 
                    res[field]['string'] = days[x-1] 
        return res 

    def fields_view_get(self, cr, uid, view_id=None, view_type='form', context=None, toolbar=False, submenu=False): 
        res = super(account_cashflow_code, self).fields_view_get(cr, uid, view_id=view_id, view_type=view_type, context=context, toolbar=toolbar, submenu=False) 
        if context.has_key('nbr_days') and view_type=='tree': 
            view_obj = etree.XML(res['arch']) 
            nbr_days = int(context.get('nbr_days'))        
            for el in view_obj: 
                if 'balance-day' in el.get('name'): 
                    day = int(el.get('name')[11:]) 
                    if day > nbr_days: 
                        el.getparent().remove(el)               
                res['arch'] = etree.tostring(view_obj)        
        return res