Where is '_DataLoaderIter' in pytorch 1.3.1?
When I use pytorch 1.3.1 with python3.7.4, like this 

import torch

from torch.utils.data.dataloader import _DataLoaderIter


Here is an errer : cannot import name '_DataLoaderIter' from 'torch.utils.data.dataloader'

How should I solve that?

Should I uninstall 1.3.1?

I found _DataLoaderIter is in dataloader.pyi :

class _DataLoaderIter:
    def __init__(self, loader: DataLoader) -&gt; None:...
    def __len__(self) -&gt; int: ...
    def __iter__(self) -&gt; _DataLoaderIter: ...
    def __next__(self) -&gt; Any: ...


But I can't find it in dataloader.py.

_DataLoaderIter does not exist any more. This code is the latest one that contains _DataLoaderIter. You can use _SingleProcessDataLoaderIter or _MultiProcessingDataLoaderIter. I don't think the .pyi file you mentioned is in version 1.3.1.
