Below is a sample interactive console session designed to show some of the basic features and functionality of the unqlite-python library. Also check out the full API documentation.

To begin, instantiate an UnQLite object. You can specify either the path to a database file, or use UnQLite as an in-memory database.

>>> from unqlite import UnQLite
>>> db = UnQLite()  # Create an in-memory database.

Key/value features

UnQLite can be used as a key/value store.

>>> db['foo'] = 'bar'  # Use as a key/value store.
>>> db['foo']  # The key/value deals in byte-strings.

>>> for i in range(4):
...     db['k%s' % i] = str(i)

>>> 'k3' in db
>>> 'k4' in db
>>> del db['k3']

>>> db.append('k2', 'XXXX')
>>> db['k2']

The database can also be iterated through directly. Note that keys are decoded while values are left as bytestrings.

>>> [item for item in db]
[('foo', b'bar'), ('k0', b'0'), ('k1', b'1'), ('k2', b'2XXXX')]

UnQLite databases support common dict APIs, such as keys(), values(), items(), and update().


For finer-grained record traversal, you can use cursors.

>>> with db.cursor() as cursor:
...     for key, value in cursor:
...         print(key, '=>', value.decode('utf8'))
k0 => 0
k1 => 1
k2 => 2XXXX

>>> with db.cursor() as cursor:
...     cursor.seek('k2')
...     print(cursor.value())

>>> with db.cursor() as cursor:
...     cursor.seek('k0')
...     print list(cursor.fetch_until('k2', include_stop_key=False))
[('k0', b'0'), ('k1', b'1')]

For more information, see the Cursor API documentation.

Document store features

In my opinion the most interesting feature of UnQLite is its JSON document store. The Jx9 scripting language is used to interact with the document store, and it is a wacky mix of C, JavaScript and PHP.

Interacting with the document store basically consists of creating a Jx9 script (you might think of it as an imperative SQL query), compiling it, and then executing it.


As of v0.8.0 the document store and collections APIs treat all strings as unicode.

>>> script = """
...     db_create('users');
...     db_store('users', $list_of_users);
...     $users_from_db = db_fetch_all('users');
... """

>>> list_of_users = [
...     {'username': 'Huey', 'age': 3},
...     {'username': 'Mickey', 'age': 5}
... ]

>>> with db.vm(script) as vm:
...     vm['list_of_users'] = list_of_users
...     vm.execute()
...     users_from_db = vm['users_from_db']

>>> users_from_db  # UnQLite assigns items in a collection an ID.
[{'username': 'Huey', 'age': 3, '__id': 0},
 {'username': 'Mickey', 'age': 5, '__id': 1}]

This is just a taste of what is possible with Jx9. More information can be found in the VM documentation.


To simplify working with JSON document collections, unqlite-python provides a light API for executing Jx9 queries on collections. A collection is an ordered list of JSON objects (records). Records can be appended, updated or deleted. be support for updates as well.

To begin working with Collection, you can use the UnQLite.collection() factory method:

>>> users = db.collection('users')
>>> users.create()  # Create the collection if it does not exist.
>>> users.exists()

You can use the Collection.store() method to add one or many records. To add a single record just pass in a python dict. To add multiple records, pass in a list of dicts. Records can be fetched and deleted by ID using fetch() and delete().

>>> users.store([
...     {'name': 'Charlie', 'color': 'green'},
...     {'name': 'Huey', 'color': 'white'},
...     {'name': 'Mickey', 'color': 'black'}])
>>> users.store({'name': 'Leslie', 'color': 'also green'})

>>> users.fetch(0)  # Fetch the first record, user with "__id" = 0.
{'__id': 0, 'color': 'green', 'name': 'Charlie'}

>>> users.delete(0)  # Delete the first record (user "__id" = 0).
>>> users.delete(users.last_record_id())  # Delete the last record.

You can retrieve all records in the collection, or specify a filtering function. The filtering function will be registered as a foreign function with the Jx9 VM and called from the VM.

>>> users.all()
[{'__id': 1, 'color': 'white', 'name': 'Huey'},
 {'__id': 2, 'color': 'black', 'name': 'Mickey'}]

>>> users.filter(lambda obj: obj['name'].startswith('H'))
[{'__id': 1, 'color': 'white', 'name': 'Huey'}]

More information can be found in the Collection documentation.


UnQLite supports transactions for file-backed databases (since transactions occur at the filesystem level, they have no effect on in-memory databases).

The easiest way to create a transaction is with the context manager:

>>> db = UnQLite('/tmp/test.db')
>>> with db.transaction():
...     db['k1'] = 'v1'
...     db['k2'] = 'v2'
>>> db['k1']

You can also use the transaction decorator which will wrap a function call in a transaction and commit upon successful execution (rolling back if an exception occurs).

>>> @db.commit_on_success
... def save_value(key, value, exc=False):
...     db[key] = value
...     if exc:
...         raise Exception('uh-oh')
>>> save_value('k3', 'v3')
>>> save_value('k3', 'vx', True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "unqlite/core.py", line 312, in wrapper
    return fn(*args, **kwargs)
  File "<stdin>", line 5, in save_value
Exception: uh-oh
>>> db['k3']

For finer-grained control you can call begin(), rollback() and commit() manually.

>>> db.begin()
>>> db['k3'] = 'v3-xx'
>>> db.commit()
>>> db['k3']