Equivalent api in fast-ai 2

Question

Previously I have fast-ai version 1. I am using the followings for training.

from fastai.basic_data import DataBunch from fastai.train import Learner from fastai.metrics import accuracy

#DataBunch takes data and internall create data loader
data = DataBunch.create(train_ds, valid_ds, bs=batch_size, path='./data')
#Learner uses Adam as default for learning
learner = Learner(data, model, loss_func=F.cross_entropy, metrics=[accuracy])
#Gradient is clipped
learner.clip = 0.1

Now I have updated to fast-ai==2.1.6 and all these fastai.basic_data, fastai.train and fastai.metrics become ModuleNotFoundError.

What are equivalent apis in fast-ai2?

Answer 1

This is one of the main differences of 2.x to 1.x.

The 2.x way of doing this is using DataBlock API. Learner receives dataloaders and not a databunch.

But if you already have datasets, you can easily create dataloaders from your datasets:

dls = DataLoaders.from_dsets(train, valid, 
  after_batch=[Normalize.from_stats(*imagenet_stats), *aug_transforms()])

Check the Siamese Tutorial if in doubt.