Note
Hopefully sqlite3dbm.dbm will be included in Python 3.0, renamed to dbm.sqlite.
This module is quite similar to the dbm module, but uses sqlite3 instead for a backend store. It also provides a small extension to the traditional dictionary interface.
The module defines the following constant and function:
Raised on sqlite3dbm-specific errors, such as protection errors. KeyError is raised for general mapping errors like specifying an incorrect key.
Accessible as sqlite3dbm.error.
Open a database and return a sqlite3dbm object. The filename argument is the path to the database file.
The optional flag argument can be:
| Value | Meaning |
|---|---|
| 'r' | Open existing database for reading only (default) |
| 'w' | Open existing database for reading and writing |
| 'c' | Open database for reading and writing, creating it if it doesn’t exist |
| 'n' | Always create a new, empty database, open for reading and writing |
The optional mode argument is the Unix mode of the file, used only when the database has to be created. It defaults to octal 0666 and respects the prevailing umask.
Accessible as sqlite3dbm.open.
The underlying object is a SqliteMap. In addition to the standard dictionary methods, such objects have the following methods:
x.__getitem__(k) <==> x[k]
>>> smap.update({'1': 'a', '2': 'b', '3': 'c'})
>>> smap['1', '2', '3']
[u'a', u'b', u'c']
>>> smap[['1', '2', '3']]
[u'a', u'b', u'c']
List based version of __getitem__(). Complement of update().
>>> smap.update({'1': 'a', '2': 'b', '3': 'c'})
>>> smap.select('1', '2', '3')
[u'a', u'b', u'c']
>>> smap.select(['1', '2', '3'])
[u'a', u'b', u'c']
>>> smap.select(['1', '2'], '3')
[u'a', u'b', u'c']
>>> smap.select(['1', '2'], ['3'])
[u'a', u'b', u'c']
>>> import sqlite3dbm
>>> db = sqlite3dbm.open('mydb.sqlite3', flag='c')
>>>
>>> # Print doesn't work, you need to do .items()
>>> db
<sqlite3dbm.dbm.SqliteMap object at 0x7f0d6ecac4d0>
>>> db.items()
[]
>>>
>>> # Acts like a regular dict
>>> db['foo'] = 'bar'
>>> db['foo']
'bar'
>>> db.items()
[('foo', 'bar')]
>>> del db['foo']
>>> db.items()
[]
>>>
>>> # Some extentions that allow for batch reads
>>> db.update({'foo': 'one', 'bar': 'two', 'baz': 'three'})
>>> db['foo', 'bar']
['one', 'two']
>>> db.select('foo', 'bar')
['one', 'two']
>>> db.select('foo', 'bar', 'qux')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "./sqlite3dbm/dbm.py", line 343, in select
raise KeyError('One of the requested keys is missing!')
KeyError: 'One of the requested keys is missing!'
>>> db.get_many('foo', 'bar', 'qux')
['one', 'two', None]
>>> db.get_many('foo', 'bar', 'qux', default='')
['one', 'two', '']
>>>
>>> # Persistent!
>>> db.items()
[('baz', 'three'), ('foo', 'one'), ('bar', 'two')]
>>> del db
>>> reopened_db = sqlite3dbm.open('mydb.sqlite3')
>>> reopened_db.items()
[('baz', 'three'), ('foo', 'one'), ('bar', 'two')]
>>>
>>> # Be aware that the default flag is 'r'
>>> reopened_db['qux'] = 'four'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "./sqlite3dbm/dbm.py", line 164, in __setitem__
raise error('DB is readonly')
sqlite3dbm.dbm.SqliteMapException: DB is readonly
>>> writeable_db = sqlite3dbm.open('mydb.sqlite3', flag='w') # 'c' would be fine too
>>> writeable_db['qux'] = 'four'
>>> reopened_db.items()
[('baz', 'three'), ('foo', 'one'), ('bar', 'two'), ('qux', 'four')]
>>> writeable_db.items()
[('baz', 'three'), ('foo', 'one'), ('bar', 'two'), ('qux', 'four')]
>>>
>>> # Catching sqlite3dbm-specific errors
>>> try:
... reopened_db['foo'] = 'blargh'
... except sqlite3dbm.error:
... print 'Caught a module-specific error'
...
Caught a module-specific error
See also