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13.10.1 Database Objects

The database objects returned by `open()` provide the methods common to all the DBM-style databases and mapping objects. The following methods are available in addition to the standard methods.

`first`( | )

  It's possible to loop over every key/value pair in the database using this method and the `next()` method. The traversal is ordered by the databases internal hash values, and won't be sorted by the key values. This method returns the starting key.

`last`( | )

  Return the last key/value pair in a database traversal. This may be used to begin a reverse-order traversal; see `previous()`.

`next`( | )

  Returns the key next key/value pair in a database traversal. The following code prints every key in the database `db`, without having to create a list in memory that contains them all:

      print db.first()
      for i in xrange(1, len(db)):
          print db.next()

`previous`( | )

  Returns the previous key/value pair in a forward-traversal of the database. In conjunction with `last()`, this may be used to implement a reverse-order traversal.

`sync`( | )

  This method forces any unwritten data to be written to the disk.