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\section{\module{anydbm} ---
Generic access to DBM-style databases}
\declaremodule{standard}{anydbm}
\modulesynopsis{Generic interface to DBM-style database modules.}
\module{anydbm} is a generic interface to variants of the DBM
database --- \refmodule{dbhash}\refstmodindex{dbhash} (requires
\refmodule{bsddb}\refbimodindex{bsddb}),
\refmodule{gdbm}\refbimodindex{gdbm}, or
\refmodule{dbm}\refbimodindex{dbm}. If none of these modules is
installed, the slow-but-simple implementation in module
\refmodule{dumbdbm}\refstmodindex{dumbdbm} will be used.
\begin{funcdesc}{open}{filename\optional{, flag\optional{, mode}}}
Open the database file \var{filename} and return a corresponding object.
If the database file already exists, the \refmodule{whichdb} module is
used to determine its type and the appropriate module is used; if it
does not exist, the first module listed above that can be imported is
used.
The optional \var{flag} argument can be
\code{'r'} to open an existing database for reading only,
\code{'w'} to open an existing database for reading and writing,
\code{'c'} to create the database if it doesn't exist, or
\code{'n'}, which will always create a new empty database. If not
specified, the default value is \code{'r'}.
The optional \var{mode} argument is the \UNIX{} mode of the file, used
only when the database has to be created. It defaults to octal
\code{0666} (and will be modified by the prevailing umask).
\end{funcdesc}
\begin{excdesc}{error}
A tuple containing the exceptions that can be raised by each of the
supported modules, with a unique exception \exception{anydbm.error} as
the first item --- the latter is used when \exception{anydbm.error} is
raised.
\end{excdesc}
The object returned by \function{open()} supports most of the same
functionality as dictionaries; keys and their corresponding values can
be stored, retrieved, and deleted, and the \method{has_key()} and
\method{keys()} methods are available. Keys and values must always be
strings.
The following example records some hostnames and a corresponding title,
and then prints out the contents of the database:
\begin{verbatim}
import anydbm
# Open database, creating it if necessary.
db = anydbm.open('cache', 'c')
# Record some values
db['www.python.org'] = 'Python Website'
db['www.cnn.com'] = 'Cable News Network'
# Loop through contents. Other dictionary methods
# such as .keys(), .values() also work.
for k, v in db.iteritems():
print k, '\t', v
# Storing a non-string key or value will raise an exception (most
# likely a TypeError).
db['www.yahoo.com'] = 4
# Close when done.
db.close()
\end{verbatim}
\begin{seealso}
\seemodule{dbhash}{BSD \code{db} database interface.}
\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{shelve}{General object persistence built on top of
the Python \code{dbm} interface.}
\seemodule{whichdb}{Utility module used to determine the type of an
existing database.}
\end{seealso}
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