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