[gdal-dev] Add to PythonGotchas: saving and closing raster datasets

[Sean Gillies]

Hi Mike,

On 5/3/14, 10:03 PM, Mike Toews wrote:
> Hi,
>
> This seems to be a common gotcha: http://gis.stackexchange.com/q/93212/1872
>
> I've been caught by it before, and I'm certain many others have too.
> This is a gotcha since "WriteArray" doesn't write the array to disk,
> but rather it is written when the dataset object is dereferenced. I've
> drafted up an entry for the wiki, which could be placed before
> "Certain objects contain a Destroy() method, but you should never use
> it".
>
> Furthermore, I'm unsure of the best way to demonstrate how to
> dereference Python objects. The wiki has two different styles:
>      obj = None
> or
>      del obj
>
> I'm unsure of which is regarded best practice, but encourage
> consistency. Please edit as necessary or reply with suggestions.
>
> -Mike

The thing is that `obj = None` and `del obj` only cause the file to be 
written (indirectly) if there are no other references to the Dataset 
object. In which case `obj = "Close!"` works just as well ;)

If your code did something like `obj2 = obj` then neither `obj = None` 
nor `del obj` will result in the file being closed because the Dataset 
object will still have a live reference (obj2).

-- 
Sean Gillies
sean at mapbox.com