Hello All,
I've recently started using PyTables and I am very excited about it's speed
and ease of use for large datasets, however, I have a problem that I have
not been able to solve with regards to user defined table attributes.
I have a table that contains observations about of entities that can be
classified as different types. The timestamp for the last observation of
these entities may be different. For processing, this table I would like to
be able to determine the timestamp of the last observation for each of
these entities. The problem is easy as long as I know the entity types.
For example:
import tables
h5file = tables.openFile('data.h5',mode='r+')
tbl = h5file.getNode('/series','data1')
last_obs = max(x['timestamp'] for x in tbl.where("""entity_type=='e1'"""))
However, my problems is that as I read from my source I may not always know
the entity type before hand. I was going to add a last_observation
attribute to my table, however, I found the link
https://github.com/PyTables/PyTables/issues/145, which says that attributes
aren't persistent. So I have two questions:
1. Are there any user-defined attributes that are persistent?
2. Does anyone have any other suggestions? Besides separating the entities
into separate tables where I could then just do a max on the timestamp
field/col?
--
Aquil H. Abdullah
aquil.abdul...@gmail.com
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