On Sep 17, 9:10 am, J Kenneth King <ja...@agentultra.com> wrote:
> ici <iltch...@gmail.com> writes:
> > I likeshelvefor saving small amounts of data, user preferences,
> > recent files etc.
> >http://docs.python.org/library/shelve.html
>
> I like it too, but I hear the great powers that be are going to
> deprecate it.
If you want the convenience of shelve without the limitations of dbm,
you can do:
"""Implementation of Python shelves using SQLite."""
from __future__ import division
import UserDict
import pickle
import sqlite3
def to_db_type(value):
"""
If value's type is supported natively in SQLite, return value.
Otherwise, return a pickled representation.
"""
if value is None or isinstance(value, (int, long, float,
basestring)):
return value
else:
return buffer(pickle.dumps(value))
def from_db_type(value):
"""
Converts a value from the database to a Python object.
"""
if isinstance(value, buffer):
return pickle.loads(value)
else:
return value
class SQLiteShelf(UserDict.DictMixin):
"""
Shelf implementation using an SQLite3 database.
"""
def __init__(self, filename):
self._database = sqlite3.connect(filename)
self._database.execute("CREATE TABLE IF NOT EXISTS Shelf "
"(Key TEXT PRIMARY KEY NOT NULL, Value
BLOB)")
self._open = True
def __del__(self):
self.close()
def __getitem__(self, key):
row = self._database.execute("SELECT Value FROM Shelf WHERE
Key=?",
[key]).fetchone()
if row:
return from_db_type(row[0])
else:
raise KeyError(key)
def __setitem__(self, key, value):
self._database.execute("INSERT OR REPLACE INTO Shelf VALUES
(?, ?)",
[key, to_db_type(value)])
def __delitem__(self, key):
self._database.execute("DELETE FROM Shelf WHERE Key=?", [key])
def keys(self):
"""Return a list of keys in the shelf."""
return [row[0] for row in
self._database.execute("SELECT Key FROM Shelf")]
def close(self):
"""Commit changes and close the file."""
if self._database is not None:
self._database.commit()
self._database.close()
self._database = None
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