'''
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 NotImplementedError
def store_put(self, key, value):
raise NotImplementedError
def store_exists(self, key):
raise NotImplementedError
def store_delete(self, key):
raise NotImplementedError
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)
