TinyKV - a minimal key-value database for Python using SQLite3

TinyKV implements a key-value database interface for Python 3 using the sqlite3 module from the standard library. There is no dependency on external packages.

TinyKV requires Python 3.7 or above.

Installation

pip install tinykv

Basic usage

First let’s import sqlite3 and the TinyKV module:

>>> import sqlite3
>>> import tinykv

TinyKV does not create a SQLite3 database to operate on. Instead, it operate on connections managed by the caller. So let’s create a database for using in the examples:

>>> conn = sqlite3.connect(':memory:')

This is how you create a TinyKV object:

>>> kv = tinykv.TinyKV(conn)
Traceback (most recent call last):
    ...
RuntimeError: Table 'kv' not found in the database

Oops... TinyKV does not create the database table it needs either. For that the application can use create_schema():

>>> tinykv.create_schema(conn)

Let’s try again:

>>> kv = tinykv.TinyKV(conn)
>>> kv  # doctest: +ELLIPSIS
<tinykv.TinyKV object at 0x...>

Now it works!

Storing and retrieving data

Use set() and get() to store and retrieve data from a TinyKV database, respectively:

>>> kv.set('foo', 'bar')
>>> kv.get('foo')
'bar'

Trying to get a nonexistent key raises KeyError:

>>> kv.get('not-there')
Traceback (most recent call last):
    ...
KeyError: 'not-there'

You can pass a default value to be returned if a key does not exist:

>>> kv.get('not-there', 'but-try-this')
'but-try-this'

Value data types

You can store any regular Python scalar in the key-value database:

>>> kv.set('foo', None)
>>> foo = kv.get('foo')
>>> foo is None
True

>>> kv.set('one', 1)
>>> kv.get('one')
1

>>> kv.set('pi', 3.1415926)
>>> kv.get('pi')
3.1415926

Same for container objects:

>>> kv.set('a_list', ['one', 'two', 'three'])
>>> kv.get('a_list')
['one', 'two', 'three']

In fact, you can store any pickable object:

>>> import datetime
>>>
>>> kv.set('a-long-time-ago', datetime.datetime(2022, 3, 19, 20, 15, 5))

>>> a_long_time_ago = kv.get('a-long-time-ago')

>>> a_long_time_ago
datetime.datetime(2022, 3, 19, 20, 15, 5)

>>> type(a_long_time_ago)
<class 'datetime.datetime'>

Removing entries

Use remove() to remove entries from the database:

>>> kv.set('foo', 'bar')
>>> kv.remove('foo')
>>> kv.get('foo')
Traceback (most recent call last):
    ...
KeyError: 'foo'

Working with multiple entries

Use set_many() with a key-value dict to store multiple entries at once:

>>> kv.set_many({
...     'one': 1,
...     'two': 2,
... })
>>> kv.get('one')
1
>>> kv.get('two')
2

Call get_many() to retrieve many entries. The function returns a dict of all keys-values found in the database:

>>> kv.set('one', 1)
>>> kv.set('two', 2)
>>> kv.get_many(['one', 'two', 'not-there'])
{'one': 1, 'two': 2}

You can also use get_glob() to fetch entries based a glob pattern:

>>> kv.set('foo:abc', 1)
>>> kv.set('foo:xyz', 2)
>>> kv.set('bar:123', 3)

>>> kv.get_glob('foo:*')
{'foo:abc': 1, 'foo:xyz': 2}

>>> kv.get_glob('*:123')
{'bar:123': 3}

Notice that get_many() and get_glob() never raise KeyError for nonexistent keys. Instead, those keys are simple not present in the returned dict.

You can also remove many entries in one call with remove_many(). Nonexistent keys are silently ignored:

>>> kv.get('one')
1

>>> kv.remove_many(['one', 'not-there'])
>>> kv.get('one')
Traceback (most recent call last):
    ...
KeyError: 'one'

Miscellaneous

• TinyKV keys must be string scalars.

• TinyKV does not open or manage transactions Also, it operates both in autocommit and non-autocommit mode. All operations are atomic.

• Naturally, if the connection handle is not in autocommit mode, you must call commit() on the connection to save the data.

• The connection handle is available in the read-only attribute conn of the TinyKV object:

    >>> kv.conn  # doctest: +ELLIPSIS
    <sqlite3.Connection object at 0x...>
  

• By default the table used by TinyKV is called kv. You can change that by passing a table argument to create_schema() and the TinyKV constructor:

    >>> CUSTOM_TABLE = 'custom_kv'
    >>>
    >>> tinykv.create_schema(conn, table=CUSTOM_TABLE)
    >>>
    >>> custom_kv = tinykv.TinyKV(conn, table=CUSTOM_TABLE)
  

Questions? Bugs? Suggestions?

Visit https://github.com/flaviovs/tinykv