[Biopython-dev] Bio.PDB - Missing values (was Moratorium on commits?)

[Lenna Peterson]

On Thu, Aug 15, 2013 at 9:23 AM, Peter Cock <p.j.a.cock at googlemail.com>wrote:
>
>
> I didn't mean to suggest writing the string "None" in the field, and
> I'm not sure if João did - it would certainly be an invalid PDB file.
>
> I agree that where the data structure has None (e.g. from our parser)
> then the writer could use a blank string (of the appropriate width).
> For mandatory fields like occupancy, this should give a warning.
>
>
As I suspected, the writer currently fails on None (it's expecting a
float). Test-driven development!

However, I don't see a simple or elegant way to force writing of a blank
occupancy. ATOM lines are currently written using C-style string
formatting, and the occupancy field is `%6.2f`.

Off the top of my head, I'd:

1. Store the original format string
2. Modify the format string to have "%6s" at the appropriate position
3. Modify the occupancy to be an empty string or a space
4. Set the return value to the formatted string
5. Restore the original format string
6. Return the return value

However, this seems...ugly at best. I don't know that switching formatting
styles (e.g. to string.format() or others) will help. And in most
circumstances, the type checking of the format string is useful.

Any thoughts?

Cheers,

Lenna