Hi everyone, as some of you know I shared implementation of Devise in fastai here
I used
dls=ImageDataLoaders.from_lists(path="./",fnames=images,labels=img_vecs,y_block=RegressionBlock,bs=256,seed=123)
to read create the dataloader, here the images are a list of image paths, and the img_vecs is the list of word vector arrays of the labels.
I wanted to use the Datablock API here but couldn’t figure out how first, but after digging the source code I came up with
def _zip(x):
return L(x).zip()
dblock=DataBlock(blocks=(ImageBlock,RegressionBlock),get_items=_zip,getters=[ItemGetter(0),ItemGetter(1)],splitter=RandomSplitter(seed=123))
dls = dblock.dataloaders((images,img_vecs))
that is exactly what happens when you use ImageDataLoaders.from_lists, but I still don’t know why get_items=_zip is needed, I’m guessing the dataloader expects each item in x,y as inputs separately rather than a batch or list of them so that it can transform them properly, stack them and return as a batch? Can anyone explain me what is happening here?