Question

I have table looks like this

------------------ 
GeneId | ProteinId
1      |    157 
2      |     - 
3      |    587     
4      |    897 
5      |     - 
6      |    120

In realational database, I can treat ProteinId column as INT and use NULL for “-” data. However, I can’t find the same option in pytables. Does pytables support NULL ? Currently, I use “0” for NULL data.

Answer 1

As the docs say,

Cells in a PyTables’ table always have
a value of the cell type, so there is
no NULL. Instead, cells take a default
value (zero or empty) which can be
changed in the type declaration, like
this: col_name = StringCol(10,
dflt=’nothing’) (col_name takes the
value ‘nothing’ if unset).

So, for integer columns, a default of 0 is normally used, and, no, alas!, there is no way to mark a value as missing or unknown, as NULL does in SQL.