ref: a8d00e5d56b261376410c3c87c46327362763bd8
dir: /sys/src/cmd/python/Doc/lib/libbastion.tex/
\section{\module{Bastion} --- Restricting access to objects} \declaremodule{standard}{Bastion} \modulesynopsis{Providing restricted access to objects.} \moduleauthor{Barry Warsaw}{[email protected]} \versionchanged[Disabled module]{2.3} \begin{notice}[warning] The documentation has been left in place to help in reading old code that uses the module. \end{notice} % I'm concerned that the word 'bastion' won't be understood by people % for whom English is a second language, making the module name % somewhat mysterious. Thus, the brief definition... --amk According to the dictionary, a bastion is ``a fortified area or position'', or ``something that is considered a stronghold.'' It's a suitable name for this module, which provides a way to forbid access to certain attributes of an object. It must always be used with the \refmodule{rexec} module, in order to allow restricted-mode programs access to certain safe attributes of an object, while denying access to other, unsafe attributes. % I've punted on the issue of documenting keyword arguments for now. \begin{funcdesc}{Bastion}{object\optional{, filter\optional{, name\optional{, class}}}} Protect the object \var{object}, returning a bastion for the object. Any attempt to access one of the object's attributes will have to be approved by the \var{filter} function; if the access is denied an \exception{AttributeError} exception will be raised. If present, \var{filter} must be a function that accepts a string containing an attribute name, and returns true if access to that attribute will be permitted; if \var{filter} returns false, the access is denied. The default filter denies access to any function beginning with an underscore (\character{_}). The bastion's string representation will be \samp{<Bastion for \var{name}>} if a value for \var{name} is provided; otherwise, \samp{repr(\var{object})} will be used. \var{class}, if present, should be a subclass of \class{BastionClass}; see the code in \file{bastion.py} for the details. Overriding the default \class{BastionClass} will rarely be required. \end{funcdesc} \begin{classdesc}{BastionClass}{getfunc, name} Class which actually implements bastion objects. This is the default class used by \function{Bastion()}. The \var{getfunc} parameter is a function which returns the value of an attribute which should be exposed to the restricted execution environment when called with the name of the attribute as the only parameter. \var{name} is used to construct the \function{repr()} of the \class{BastionClass} instance. \end{classdesc}