How to make batch predictions in fastai

predict_batch.py

@patch
def predict_batch(self:Learner, item, rm_type_tfms=None, with_input=False):
    dl = self.dls.test_dl(item, rm_type_tfms=rm_type_tfms, num_workers=0)
    inp,preds,_,dec_preds = self.get_preds(dl=dl, with_input=True, with_decoded=True)
    i = getattr(self.dls, 'n_inp', -1)
    inp = (inp,) if i==1 else tuplify(inp)
    dec_inp, nm = zip(*self.dls.decode_batch(inp + tuplify(dec_preds)))
    res = preds,nm,dec_preds
    if with_input: res = (dec_inp,) + res
    return res

Actually, this prediction method works for both:

def predict(self, item, rm_type_tfms=None, with_input=False):
    dl = self.dls.test_dl(item, rm_type_tfms=rm_type_tfms, num_workers=0)
    inp,preds,_,dec_preds = self.get_preds(dl=dl, with_input=True, with_decoded=True)
    i = getattr(self.dls, 'n_inp', -1)
    inp = (inp,) if i==1 else tuplify(inp)
    dec = self.dls.decode_batch(inp + tuplify(dec_preds))
    dec_inp,dec_targ = (tuple(map(detuplify, d)) for d in zip(*dec.map(lambda x: (x[:i], x[i:]))))
    res = dec_targ,dec_preds,preds
    if with_input: res = (dec_inp,) + res
    return res

Other notes h/t zach:

learn.dls.vocab or learn.dls.categorize.vocab is another way to get the class names.