报错Can‘t pickle ＜function ＜lambda＞ at……

使用pytorch的DataLoader后，在取出样本时报错

_pickle.PicklingError: Can't pickle <function <lambda> at 0x000002573E340E58>: attribute lookup <lambda> on __main__ failed

问题原因：在设置DataLoader时，设置了num_workers=1

torch.utils.data.DataLoader(
        mat_dataset,
        batch_size=1, shuffle=False,
        num_workers=1, pin_memory=opt.no_cuda
    )

将num_workers设置为0解决问题

torch.utils.data.DataLoader(
        mat_dataset,
        batch_size=1, shuffle=False,
        num_workers=0, pin_memory=opt.no_cuda
    )