What's meaning of dim "none"?

Course Q&A Deep Learning Specialization Sequence Models
1

Hi guys and mentors,

In the section of djmodel, from Jazz hw.

what’s the meaning of dim none? batch size?
for example:
image

or, after using the function reshape:

image
image1062×255 25.8 KB

so, after you reshape something, new dim (batch size) will be introduced? I want to reshape to 2D (3, 4) and final output will be 3D (None, 3, 4) ? wow… thank you.

2

In that context, “None” means that the dimension is not being defined in that line of code. Some other line of code will define that variable later.

3

yeah, you are right. I googled about this. I am not 100% clear when this should be introduced, but it seems like this 1st dim is the batch size… thank you.