PIL's thumbnail function returns NoneType

[Mirat Can Bayrak]

Can you try it? it is about me or it is a bug?

In [1]: import Image

In [2]: im = Image.open("r.png")

In [3]: type(im)
Out[3]: <type 'instance'>

In [4]: thm = im.thumbnail((200,200))

In [5]: type(thm)
Out[5]: <type 'NoneType'>

 

[Hrvoje Niksic]

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.

In [4]: thm = im.thumbnail((200,200))

In [5]: type(thm)
Out[5]: <type 'NoneType'>

Instead of thm, simply keep using ihm.

 

[Terry Reedy]

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.