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