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# Copyright (c) 2006,2007 Mitch Garnaat http://garnaat.org/
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
import base64
class Item(dict):
"""
A ``dict`` sub-class that serves as an object representation of a
SimpleDB item. An item in SDB is similar to a row in a relational
database. Items belong to a :py:class:`Domain <boto.sdb.domain.Domain>`,
which is similar to a table in a relational database.
The keys on instances of this object correspond to attributes that are
stored on the SDB item.
.. tip:: While it is possible to instantiate this class directly, you may
want to use the convenience methods on :py:class:`boto.sdb.domain.Domain`
for that purpose. For example, :py:meth:`boto.sdb.domain.Domain.get_item`.
"""
def __init__(self, domain, name='', active=False):
"""
:type domain: :py:class:`boto.sdb.domain.Domain`
:param domain: The domain that this item belongs to.
:param str name: The name of this item. This name will be used when
querying for items using methods like
:py:meth:`boto.sdb.domain.Domain.get_item`
"""
dict.__init__(self)
self.domain = domain
self.name = name
self.active = active
self.request_id = None
self.encoding = None
self.in_attribute = False
self.converter = self.domain.connection.converter
def startElement(self, name, attrs, connection):
if name == 'Attribute':
self.in_attribute = True
self.encoding = attrs.get('encoding', None)
return None
def decode_value(self, value):
if self.encoding == 'base64':
self.encoding = None
return base64.decodestring(value)
else:
return value
def endElement(self, name, value, connection):
if name == 'ItemName':
self.name = self.decode_value(value)
elif name == 'Name':
if self.in_attribute:
self.last_key = self.decode_value(value)
else:
self.name = self.decode_value(value)
elif name == 'Value':
if self.last_key in self:
if not isinstance(self[self.last_key], list):
self[self.last_key] = [self[self.last_key]]
value = self.decode_value(value)
if self.converter:
value = self.converter.decode(value)
self[self.last_key].append(value)
else:
value = self.decode_value(value)
if self.converter:
value = self.converter.decode(value)
self[self.last_key] = value
elif name == 'BoxUsage':
try:
connection.box_usage += float(value)
except:
pass
elif name == 'RequestId':
self.request_id = value
elif name == 'Attribute':
self.in_attribute = False
else:
setattr(self, name, value)
def load(self):
"""
Loads or re-loads this item's attributes from SDB.
.. warning::
If you have changed attribute values on an Item instance,
this method will over-write the values if they are different in
SDB. For any local attributes that don't yet exist in SDB,
they will be safe.
"""
self.domain.get_attributes(self.name, item=self)
def save(self, replace=True):
"""
Saves this item to SDB.
:param bool replace: If ``True``, delete any attributes on the remote
SDB item that have a ``None`` value on this object.
"""
self.domain.put_attributes(self.name, self, replace)
# Delete any attributes set to "None"
if replace:
del_attrs = []
for name in self:
if self[name] == None:
del_attrs.append(name)
if len(del_attrs) > 0:
self.domain.delete_attributes(self.name, del_attrs)
def add_value(self, key, value):
"""
Helps set or add to attributes on this item. If you are adding a new
attribute that has yet to be set, it will simply create an attribute
named ``key`` with your given ``value`` as its value. If you are
adding a value to an existing attribute, this method will convert the
attribute to a list (if it isn't already) and append your new value
to said list.
For clarification, consider the following interactive session:
.. code-block:: python
>>> item = some_domain.get_item('some_item')
>>> item.has_key('some_attr')
False
>>> item.add_value('some_attr', 1)
>>> item['some_attr']
1
>>> item.add_value('some_attr', 2)
>>> item['some_attr']
[1, 2]
:param str key: The attribute to add a value to.
:param object value: The value to set or append to the attribute.
"""
if key in self:
# We already have this key on the item.
if not isinstance(self[key], list):
# The key isn't already a list, take its current value and
# convert it to a list with the only member being the
# current value.
self[key] = [self[key]]
# Add the new value to the list.
self[key].append(value)
else:
# This is a new attribute, just set it.
self[key] = value
def delete(self):
"""
Deletes this item in SDB.
.. note:: This local Python object remains in its current state
after deletion, this only deletes the remote item in SDB.
"""
self.domain.delete_item(self)
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