Cannot install Python 3.7 on osx-arm64

Question

I am trying to create a new environment with Python 3.7 using Conda like:

conda create -n qnn python=3.7 

I got following errors:

Collecting package metadata (current_repodata.json): done
Solving environment: failed with repodata from current_repodata.json, will retry with next repodata source.
Collecting package metadata (repodata.json): done
Solving environment: failed

PackagesNotFoundError: The following packages are not available from current channels:

  - python==3.7

Current channels:

  - https://conda.anaconda.org/conda-forge/osx-arm64
  - https://conda.anaconda.org/conda-forge/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.

Why is Python 3.7 apparently unavailable?

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System Details

This is on an Apple Silicon (osx-arm64) machine running macOS.

Answer 1

No native builds available

Since Python 3.8 had been released for about a year when Apple Silicon hit the market, Python 3.7 builds for osx-arm64 were never part of the regular build matrix for Conda Forge.

Workaround: Emulate

Immediate alternatives for using 3.7 on Apple Silicon systems would be to emulate x86_64 with Rosetta or use a container system, e.g., Docker.

Creating osx-64 environments

Similar to what one does for running win-32 environments on x86_64 machines, one can create osx-64 environments like

## create empty environment
conda create -n py37

## activate
conda activate py37

## use x86_64 architecture channel(s)
conda config --env --set subdir osx-64

## install python, numpy, etc. (add more packages here...)
conda install python=3.7 numpy

?? Important Note: Be sure to always activate this environment before installing packages. Otherwise, the default CONDA_SUBDIR value (osx-arm64) may be active and could result in mixing architectures in the same environment.

Note that MacOS will automatically recognize the architecture and run through Rosetta - one need not do anything special.

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Requesting native build

Longer term, you could try requesting that the python-feedstock include a 3.7 build for osx-arm64. However, 3.7.12 (Sept. 2021) was technically the final feature release, and it has now entered the maintenance-only phase (see PEP 537). Also, other packages that build Python-version-specific variants would not be built for osx-arm64, so even if one had python=3.7, the packages wouldn't be there (at least not through Conda). Basically, I wouldn't bet on anyone taking this up.

Answer 2

Not sure if this is the best strategy, but running

CONDA_SUBDIR=osx-64 conda

worked for my use case.