PIL's thumbnail function returns NoneType

Terry Reedy tjreedy at udel.edu
Sun Mar 1 22:47:34 CET 2009

Hrvoje Niksic wrote:
> Mirat Can Bayrak <miratcanbayrak at gmail.com> writes:
>> Can you try it? it is about me or it is a bug?
> Neither.  im.thumbnail() modifies the existing image object by
> converting it to a thumbnail.  In Python such methods by convention
> return None.
> The documentation explicitly mentions that:
>     Also note that this function modifies the Image object in
>     place. If you need to use the full resolution image as well, apply
>     this method to a copy of the original image. This method returns
>     None.

Indeed, the purpose of returning None is to remind that the method does 
mutation in place.

>> In [4]: thm = im.thumbnail((200,200))
>> In [5]: type(thm)
>> Out[5]: <type 'NoneType'>
> Instead of thm, simply keep using ihm.
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