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# Version 1 UUIDs (TimeUUIDType)

Version 1 UUIDs are frequently used for timelines instead of timestamps. Normally, this makes it difficult to get a slice of columns for some time range or to create a column name or value for some specific time.

To make this easier, if a `datetime` object or a timestamp with the same precision as the output of `time.time()` is passed where a TimeUUID is expected, pycassa will convert that into a `uuid.UUID` with an equivalent timestamp component.

Suppose we have something like Twissandra’s public timeline but with TimeUUIDs for column names. If we want to get all tweets that happened yesterday, we can do:

    >>> import datetime
    >>> line = pycassa.ColumnFamily(pool, 'Userline')
    >>> today = datetime.datetime.utcnow()
    >>> yesterday = today - datetime.timedelta(days=1)
    >>> tweets = line.get('__PUBLIC__', column_start=yesterday, column_finish=today)

Now, suppose there was a tweet that was supposed to be posted on December 11th at 8:02:15, but it was dropped and now we need to put it in the public timeline. There’s no need to generate a UUID, we can just pass another datetime object instead:

    >>> from datetime import datetime
    >>> line = pycassa.ColumnFamily(pool, 'Userline')
    >>> time = datetime(2010, 12, 11, 8, 2, 15)
    >>> line.insert('__PUBLIC__', {time: 'some tweet stuff here'})

One limitation of this is that you can’t ask for one specific column with a TimeUUID name by passing a `datetime` through something like the columns parameter for `get()`; this is because there is no way to know the non-timestamp components of the UUID ahead of time. Instead, simply pass the same `datetime` object for both column_start and column_finish and you’ll get one or more columns for that exact moment in time.

Note that Python does not sort UUIDs the same way that Cassandra does. When Cassandra sorts V1 UUIDs it first compares the time component, and then the raw bytes of the UUID. Python on the other hand just sorts the raw bytes. If you need to sort UUIDs in Python the same way Cassandra does you will want to use something like this:

    >>> import uuid, random
    >>> uuids = [uuid.uuid1() for _ xrange(10)]
    >>> random.shuffle(uuids)
    >>> improperly_sorted = sorted(uuids)
    >>> properly_sorted = sorted(uuids, key=lambda k: (k.time, k.bytes))

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