Re: [Pytables-users] Update a table.

[Vicent M. <uv...@on...>]

Hi again Ahmad,

El Wednesday 16 June 2004 17:18, Ahmad Hosseinzadeh escribio:
> Hi,
>
> I'm new to PyTables.
> I don't know how to declare a string field with
> variable length in my tables.

You cannot. In a table object rows are defined inheriting the IsDescription 
class. This class, in turn, uses Col classes to declare the fields of the 
row. In particular fields of type string are declared using the StringCol 
class. As you can see in the manual (section 4.11.2) the very first parameter 
of the class constructor fixes the length of the string, so no variable 
length strings are available. However they can be simulated setting the 
length parameter to the maximum length you need. The reason is that when 
strings are read they just use its original size, not the maximum size given 
to the constructor.
Hopefully support for tables with variable length of fields (VLTable) will be 
included in the release 1.0 of pytables.

> Also I have problem with updating a table or array.
> I want to update a record of my table (PyTables) but I
> don't know how.
> I have the same problem with arrays in PyTables.

Updates are not yet supported. You will have to wait to release 0.9

> My solution is to remove the previous one and create a
> new record or array but it is not efficient.
> Can anyone help me?
>
> Thanks.
> Ahmad.
>

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