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Diffstat (limited to 'Doc/lib/libshelve.tex')
| -rw-r--r-- | Doc/lib/libshelve.tex | 31 |
1 files changed, 18 insertions, 13 deletions
diff --git a/Doc/lib/libshelve.tex b/Doc/lib/libshelve.tex index 7a463cd..6b96872 100644 --- a/Doc/lib/libshelve.tex +++ b/Doc/lib/libshelve.tex @@ -1,5 +1,5 @@ \section{\module{shelve} --- - Python object persistency.} + Python object persistency} \declaremodule{standard}{shelve} \modulesynopsis{Python object persistency.} @@ -8,8 +8,8 @@ A ``shelf'' is a persistent, dictionary-like object. The difference with ``dbm'' databases is that the values (not the keys!) in a shelf can be essentially arbitrary Python objects --- anything that the -\code{pickle} module can handle. This includes most class instances, -recursive data types, and objects containing lots of shared +\refmodule{pickle} module can handle. This includes most class +instances, recursive data types, and objects containing lots of shared sub-objects. The keys are ordinary strings. \refstmodindex{pickle} @@ -32,20 +32,20 @@ list = d.keys() # a list of all existing keys (slow!) d.close() # close it \end{verbatim} -% + Restrictions: \begin{itemize} \item -The choice of which database package will be used (e.g. \code{dbm} or -\code{gdbm}) -depends on which interface is available. Therefore it isn't safe to -open the database directly using \code{dbm}. The database is also -(unfortunately) subject to the limitations of \code{dbm}, if it is used --- -this means that (the pickled representation of) the objects stored in -the database should be fairly small, and in rare cases key collisions -may cause the database to refuse updates. +The choice of which database package will be used +(e.g. \refmodule{dbm} or \refmodule{gdbm}) depends on which interface +is available. Therefore it is not safe to open the database directly +using \refmodule{dbm}. The database is also (unfortunately) subject +to the limitations of \refmodule{dbm}, if it is used --- this means +that (the pickled representation of) the objects stored in the +database should be fairly small, and in rare cases key collisions may +cause the database to refuse updates. \refbimodindex{dbm} \refbimodindex{gdbm} @@ -54,7 +54,7 @@ Dependent on the implementation, closing a persistent dictionary may or may not be necessary to flush changes to disk. \item -The \code{shelve} module does not support \emph{concurrent} read/write +The \module{shelve} module does not support \emph{concurrent} read/write access to shelved objects. (Multiple simultaneous read accesses are safe.) When a program has a shelf open for writing, no other program should have it open for reading or writing. \UNIX{} file locking can @@ -65,6 +65,11 @@ requires knowledge about the database implementation used. \begin{seealso} + \seemodule{anydbm}{Generic interface to \code{dbm}-style databases.} + % Should include entry for dbhash, but that isn't documented. + \seemodule{dbm}{Standard \UNIX{} database interface.} + \seemodule{dumbdbm}{Portable implementation of the \code{dbm} interface.} + \seemodule{gdbm}{GNU database interface, based on the \code{dbm} interface.} \seemodule{pickle}{Object serialization used by \module{shelve}.} \seemodule{cPickle}{High-performance version of \module{pickle}.} \end{seealso} |