I'm trying to install specific PyTorch version under conda env:

Using pip:

pip3 install pytorch==1.0.1
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue.
To avoid this problem you can invoke Python with '-m pip' instead of running pip directly.
Defaulting to user installation because normal site-packages is not writeable
ERROR: Could not find a version that satisfies the requirement pytorch==1.0.1 (from versions: 0.1.2, 1.0.2)
ERROR: No matching distribution found for pytorch==1.0.1

Using Conda:

conda install pytorch==1.0.1
    Collecting package metadata (current_repodata.json): done
    Solving environment: failed with initial frozen solve. Retrying with flexible solve.
    Collecting package metadata (repodata.json): done
    Solving environment: failed with initial frozen solve. Retrying with flexible solve.
    
    PackagesNotFoundError: The following packages are not available from current channels:
    
      - pytorch==1.0.1
    
    Current channels:
    
      - https://repo.anaconda.com/pkgs/main/osx-64
      - https://repo.anaconda.com/pkgs/main/noarch
      - https://repo.anaconda.com/pkgs/r/osx-64
      - https://repo.anaconda.com/pkgs/r/noarch
    
    To search for alternate channels that may provide the conda package you're
    looking for, navigate to
    
        https://anaconda.org
    
    and use the search bar at the top of the page.

This works for me:

conda install pytorch==1.7.1 torchvision cudatoolkit=10.2 -c pytorch

note I also specified the cuda version too.

Note this was asked on the pytorch forum too: https://discuss.pytorch.org/t/how-to-switch-to-older-version-of-pytorch/19656/21

# CUDA 9.0
conda install pytorch==1.0.1 torchvision==0.2.2 cudatoolkit=9.0 -c pytorch

# CUDA 10.0
conda install pytorch==1.0.1 torchvision==0.2.2 cudatoolkit=10.0 -c pytorch

# CPU Only
conda install pytorch-cpu==1.0.1 torchvision-cpu==0.2.2 cpuonly -c pytorch 

pip install torch==1.8.1+cu102 torchvision==0.9.1+cu102 torchaudio===0.8.1 -f https://download.pytorch.org/whl/torch_stable.html

pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org torch===0.4.1 torchvision===0.4.2 -f https://download.pytorch.org/whl/torch_stable.html​