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A Dijous 14 Juny 2007 14:39, escriguéreu: > Hi, > > I'm new to pytables and would like to work with tables which have > multiple columns with variable length strings. This seems like a > common use case, but as most of the examples in the manual deal with > fixed-length strings I was wondering what the best practices are for > this situation. There are a few possibilities which occurred to me: > > 1) Make a group in which fixed width columns are kept in one table, > with separate VLArrays for each of the variable length columns using > the VLStringAtom(). Disadvantage: now the data is spread over the > place in multiple variables and the number of rows in the main table > and the individual VLArrays are not constrained to be the same. > > 2) Make a VLArray with an ObjectAtom for each row. Then encode each > row in the table as a single python object. Disadvantage: while > possible, now you can't do any kind of indexing and the benefits of > keeping the data in pytables format are less apparent. > > 3) Truncate variable length strings by estimating a maximum length of > each string, thereby forcing the data into a standard table with > fixed length StringCols. Disadvantage: This is a hack as it's not > always obvious what the maximum length will be. Moreover, space would > be wasted as most strings are much less than the maximum length. > > The basic issue is that VLStringCol does not exist. I understand the > reasons for this (it breaks the concept of having a fixed-width > record length, unless you use a pointer in the record), but is there > any available workaround? E.g. is there any way to nest multiple > VLArray objects in a table? > > Thanks in advance for any advice you can offer. > > --Balaji > > > PS: When is Pytables Pro scheduled to be released? The website says > April 2007, but I haven't seen any recent postings about it. > > > -- > Balaji S. Srinivasan, Ph.D. > Stanford University > Lecturer, Depts. of Statistics and Computer Science > 318 Campus Drive, Clark Center S251 > (650) 380-0695 > [EMAIL PROTECTED] > http://jinome.stanford.edu ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
