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| 1 | +\section{Standard Module \sectcode{Bastion}} |
| 2 | +\stmodindex{Bastion} |
| 3 | +\renewcommand{\indexsubitem}{(in module Bastion)} |
| 4 | + |
| 5 | +% I'm concerned that the word 'bastion' won't be understood by people |
| 6 | +% for whom English is a second language, making the module name |
| 7 | +% somewhat mysterious. Thus, the brief definition... --amk |
| 8 | + |
| 9 | +According to the dictionary, a bastion is ``a fortified area or |
| 10 | +position'', or ``something that is considered a stronghold.'' It's a |
| 11 | +suitable name for this module, which provides a way to forbid access |
| 12 | +to certain attributes of an object. It must always be used with the |
| 13 | +\code{rexec} module, in order to allow restricted-mode programs access |
| 14 | +to certain safe attributes of an object, while denying access to |
| 15 | +other, unsafe attributes. |
| 16 | + |
| 17 | +% I've punted on the issue of documenting keyword arguments for now. |
| 18 | + |
| 19 | +\begin{funcdesc}{Bastion}{object\optional{\, filter\, name\, class}} |
| 20 | +Protect the class instance \var{object}, returning a bastion for the |
| 21 | +object. Any attempt to access one of the object's attributes will |
| 22 | +have to be approved by the \var{filter} function; if the access is |
| 23 | +denied an AttributeError exception will be raised. |
| 24 | + |
| 25 | +If present, \var{filter} must be a function that accepts a string |
| 26 | +containing an attribute name, and returns true if access to that |
| 27 | +attribute will be permitted; if \var{filter} returns false, the access |
| 28 | +is denied. The default filter denies access to any function beginning |
| 29 | +with an underscore (\code{_}). The bastion's string representation |
| 30 | +will be \code{<Bastion for \var{name}>} if a value for |
| 31 | +\var{name} is provided; otherwise, \code{repr(\var{object})} will be used. |
| 32 | + |
| 33 | +\var{class}, if present, would be a subclass of \code{BastionClass}; |
| 34 | +see the code in \file{bastion.py} for the details. Overriding the |
| 35 | +default \code{BastionClass} will rarely be required. |
| 36 | + |
| 37 | +\end{funcdesc} |
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