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Source code for kivy.storage

'''
Storage
=======

.. versionadded:: 1.7.0

.. warning::

    This module is still experimental, and the API is subject to change in a
    future version.

Usage
-----

The idea behind the Storage module is to be able to load/store any number of
key-value pairs via an indexed key. The default model is abstract so you
cannot use it directly. We provide some implementations such as:

- :class:`kivy.storage.dictstore.DictStore`: use a python dict as a store
- :class:`kivy.storage.jsonstore.JsonStore`: use a
  `JSON <https://en.wikipedia.org/wiki/JSON>`_ file as a store
- :class:`kivy.storage.redisstore.RedisStore`: use a `Redis <http://redis.io>`_
  database with `redis-py <https://github.com/andymccurdy/redis-py>`_


Examples
--------

For example, let's use a JsonStore::

    from kivy.storage.jsonstore import JsonStore

    store = JsonStore('hello.json')

    # put some values
    store.put('tito', name='Mathieu', org='kivy')
    store.put('tshirtman', name='Gabriel', age=27)

    # using the same index key erases all previously added key-value pairs
    store.put('tito', name='Mathieu', age=30)

    # get a value using a index key and key
    print('tito is', store.get('tito')['age'])

    # or guess the key/entry for a part of the key
    for item in store.find(name='Gabriel'):
        print('tshirtmans index key is', item[0])
        print('his key value pairs are', str(item[1]))

Because the data is persistent, you can check later to see if the key exists::

    from kivy.storage.jsonstore import JsonStore

    store = JsonStore('hello.json')
    if store.exists('tito'):
        print('tite exists:', store.get('tito'))
        store.delete('tito')


Synchronous / Asynchronous API
------------------------------

All the standard methods (:meth:`~AbstractStore.get`,
:meth:`~AbstractStore.put` , :meth:`~AbstractStore.exists`,
:meth:`~AbstractStore.delete`, :meth:`~AbstractStore.find`) have an
asynchronous version.

For example, the *get* method has a `callback` parameter. If set, the
`callback` will be used to return the result to the user when available:
the request will be asynchronous. If the `callback` is None, then the
request will be synchronous and the result will be returned directly.


Without callback (Synchronous API)::

    entry = mystore.get('tito')
    print('tito =', entry)

With callback (Asynchronous API)::

    def my_callback(store, key, result):
        print('the key', key, 'has a value of', result)
    mystore.get('plop', callback=my_callback)


The callback signature (for almost all methods) is::

    def callback(store, key, result):
        """
        store: the `Store` instance currently used.
        key: the key sought for.
        result: the result of the lookup for the key.
        """


Synchronous container type
--------------------------

The storage API emulates the container type for the synchronous API::

    store = JsonStore('hello.json')

    # original: store.get('tito')
    store['tito']

    # original: store.put('tito', name='Mathieu')
    store['tito'] = {'name': 'Mathieu'}

    # original: store.delete('tito')
    del store['tito']

    # original: store.count()
    len(store)

    # original: store.exists('tito')
    'tito' in store

    # original: for key in store.keys()
    for key in store:
        pass

'''

from kivy.clock import Clock
from kivy.event import EventDispatcher


[docs]class AbstractStore(EventDispatcher): '''Abstract class used to implement a Store ''' def __init__(self, **kwargs): super(AbstractStore, self).__init__(**kwargs) self.store_load()
[docs] def exists(self, key): '''Check if a key exists in the store. ''' return self.store_exists(key)
[docs] def async_exists(self, callback, key): '''Asynchronous version of :meth:`exists`. :Callback arguments: `store`: :class:`AbstractStore` instance Store instance `key`: string Name of the key to search for `result`: boo Result of the query, None if any error ''' self._schedule(self.store_exists_async, key=key, callback=callback)
[docs] def get(self, key): '''Get the key-value pairs stored at `key`. If the key is not found, a `KeyError` exception will be thrown. ''' return self.store_get(key)
[docs] def async_get(self, callback, key): '''Asynchronous version of :meth:`get`. :Callback arguments: `store`: :class:`AbstractStore` instance Store instance `key`: string Name of the key to search for `result`: dict Result of the query, None if any error ''' self._schedule(self.store_get_async, key=key, callback=callback)
[docs] def put(self, key, **values): '''Put new key-value pairs (given in *values*) into the storage. Any existing key-value pairs will be removed. ''' need_sync = self.store_put(key, values) if need_sync: self.store_sync() return need_sync
[docs] def async_put(self, callback, key, **values): '''Asynchronous version of :meth:`put`. :Callback arguments: `store`: :class:`AbstractStore` instance Store instance `key`: string Name of the key to search for `result`: bool Indicate True if the storage has been updated, or False if nothing has been done (no changes). None if any error. ''' self._schedule(self.store_put_async, key=key, value=values, callback=callback)
[docs] def delete(self, key): '''Delete a key from the storage. If the key is not found, a `KeyError` exception will be thrown.''' need_sync = self.store_delete(key) if need_sync: self.store_sync() return need_sync
[docs] def async_delete(self, callback, key): '''Asynchronous version of :meth:`delete`. :Callback arguments: `store`: :class:`AbstractStore` instance Store instance `key`: string Name of the key to search for `result`: bool Indicate True if the storage has been updated, or False if nothing has been done (no changes). None if any error. ''' self._schedule(self.store_delete_async, key=key, callback=callback)
[docs] def find(self, **filters): '''Return all the entries matching the filters. The entries are returned through a generator as a list of (key, entry) pairs where *entry* is a dict of key-value pairs :: for key, entry in store.find(name='Mathieu'): print('key:', key, ', entry:', entry) Because it's a generator, you cannot directly use it as a list. You can do:: # get all the (key, entry) availables entries = list(store.find(name='Mathieu')) # get only the entry from (key, entry) entries = list((x[1] for x in store.find(name='Mathieu'))) ''' return self.store_find(filters)
[docs] def async_find(self, callback, **filters): '''Asynchronous version of :meth:`find`. The callback will be called for each entry in the result. :Callback arguments: `store`: :class:`AbstractStore` instance Store instance `key`: string Name of the key to search for, or None if we reach the end of the results `result`: bool Indicate True if the storage has been updated, or False if nothing has been done (no changes). None if any error. ''' self._schedule(self.store_find_async, callback=callback, filters=filters)
[docs] def keys(self): '''Return a list of all the keys in the storage. ''' return self.store_keys()
[docs] def async_keys(self, callback): '''Asynchronously return all the keys in the storage. ''' self._schedule(self.store_keys_async, callback=callback)
[docs] def count(self): '''Return the number of entries in the storage. ''' return self.store_count()
[docs] def async_count(self, callback): '''Asynchronously return the number of entries in the storage. ''' self._schedule(self.store_count_async, callback=callback)
[docs] def clear(self): '''Wipe the whole storage. ''' return self.store_clear()
[docs] def async_clear(self, callback): '''Asynchronous version of :meth:`clear`. ''' self._schedule(self.store_clear_async, callback=callback)
# # Operators # def __setitem__(self, key, values): if not isinstance(values, dict): raise Exception('Only dict are accepted for the store[key] = dict') self.put(key, **values) def __getitem__(self, key): return self.get(key) def __delitem__(self, key): return self.keys() def __contains__(self, key): return self.exists(key) def __len__(self): return self.count() def __iter__(self): for key in self.keys(): yield key # # Used for implementation # def store_load(self): pass def store_sync(self): pass def store_get(self, key): raise NotImplemented() def store_put(self, key, value): raise NotImplemented() def store_exists(self, key): raise NotImplemented() def store_delete(self, key): raise NotImplemented() def store_find(self, filters): return [] def store_keys(self): return [] def store_count(self): return len(self.store_keys()) def store_clear(self): for key in self.store_keys(): self.store_delete(key) self.store_sync() def store_get_async(self, key, callback): try: value = self.store_get(key) callback(self, key, value) except KeyError: callback(self, key, None) def store_put_async(self, key, value, callback): try: value = self.put(key, **value) callback(self, key, value) except: callback(self, key, None) def store_exists_async(self, key, callback): try: value = self.store_exists(key) callback(self, key, value) except: callback(self, key, None) def store_delete_async(self, key, callback): try: value = self.delete(key) callback(self, key, value) except: callback(self, key, None) def store_find_async(self, filters, callback): for key, entry in self.store_find(filters): callback(self, filters, key, entry) callback(self, filters, None, None) def store_count_async(self, callback): try: value = self.store_count() callback(self, value) except: callback(self, 0) def store_keys_async(self, callback): try: keys = self.store_keys() callback(self, keys) except: callback(self, []) def store_clear_async(self, callback): self.store_clear() callback(self) # # Privates # def _schedule(self, cb, **kwargs): # XXX not entirely sure about the best value (0 or -1). Clock.schedule_once(lambda dt: cb(**kwargs), 0)