/usr/share/pyshared/pytools/diskdict.py is in python-pytools 2011.5-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 | # see end of file for sqlite import
class DiskDict(object):
"""Provides a disk-backed dictionary. Unlike L{shelve}, this class allows
arbitrary values for keys, at a slight performance penalty.
Note that this is a dangerous game: The C{hash()} of many objects changes
between runs. In particular, C{hash(None)} changes between runs.
C{str}, C{unicode}, C{int}, C{tuple} and C{long} seem to be constant
for a given Python executable, but they may change for a new version.
So don't use this class for data that you absolutely *have* to be able
to retrieve. It's fine for caches and the like, though.
"""
def __init__(self, dbfilename, version_base=(), dep_modules=[]):
self.db_conn = sqlite.connect(dbfilename, timeout=30)
try:
self.db_conn.execute("select * from data;")
except sqlite.OperationalError:
self.db_conn.execute("""
create table data (
id integer primary key autoincrement,
key_hash integer,
key_pickle blob,
version_hash integer,
version_pickle blob,
when_inserted timestamp default current_timestamp,
result_pickle blob)""")
def mtime(file):
if not isinstance(file, basestring):
# assume file names a module
file = file.__file__
import os
return os.stat(file).st_mtime
from cPickle import dumps
self.version = (version_base,) + tuple(
mtime(dm) for dm in dep_modules)
self.version_pickle = dumps(self.version)
self.version_hash = hash(self.version)
self.cache = {}
def __contains__(self, key):
if key in self.cache:
return True
else:
from cPickle import loads
for key_pickle, version_pickle, result_pickle in self.db_conn.execute(
"select key_pickle, version_pickle, result_pickle from data"
" where key_hash = ? and version_hash = ?",
(hash(key), self.version_hash)):
if loads(str(key_pickle)) == key and loads(str(version_pickle)) == self.version:
result = loads(str(result_pickle))
self.cache[key] = result
return True
return False
def __getitem__(self, key):
try:
return self.cache[key]
except KeyError:
from cPickle import loads
for key_pickle, version_pickle, result_pickle in self.db_conn.execute(
"select key_pickle, version_pickle, result_pickle from data"
" where key_hash = ? and version_hash = ?",
(hash(key), self.version_hash)):
if loads(str(key_pickle)) == key and loads(str(version_pickle)) == self.version:
result = loads(str(result_pickle))
self.cache[key] = result
return result
raise KeyError(key)
def __delitem__(self, key):
if key in self.cache:
del self.cache[key]
from cPickle import loads
for item_id, key_pickle, version_pickle in self.db_conn.execute(
"select id, key_pickle, version_pickle from data"
" where key_hash = ? and version_hash = ?",
(hash(key), self.version_hash)):
if loads(key_pickle) == key and loads(version_pickle) == self.version:
self.db_conn.execute("delete from data where id = ?", (item_id,))
self.db_conn.commit()
def __setitem__(self, key, value):
del self[key]
self.cache[key] = value
from cPickle import dumps
self.db_conn.execute("insert into data"
" (key_hash, key_pickle, version_hash, version_pickle, result_pickle)"
" values (?,?,?,?,?)",
(hash(key), sqlite.Binary(dumps(key)),
self.version_hash, self.version_pickle,
sqlite.Binary(dumps(value))))
self.db_conn.commit()
try:
import sqlite3 as sqlite
except ImportError:
try:
from pysqlite2 import dbapi2 as sqlite
except ImportError:
import warnings
warnings.warn("DiskDict will memory-only: "
"a usable version of sqlite was not found.")
DiskDict = dict
|