Installation of earlier versions of Python (prior to 3.8) fails on Mac with M1 Chip (ARM based Apple Silicon)

I have Macbook with Apple M1 Chip in which I have to use Python 3.6.5 for my project. It comes with Python 2.7.16 and 3.8.2 preinstalled. I used brew to install Python which by default installed 3.9.1.

So, I tried this homebrew formula to install 3.6.5, but got following error:

checking for pthread_t... yes
checking size of pthread_t... 8
configure: error: Unexpected output of 'arch' on OSX

Do not report this issue to Homebrew/brew or Homebrew/core!

I tried pyenv install 3.6.5 , but it fails with similar error as above. Method explained here by ePi272314 to install python with git commit fails because it is no longer supported in homebrew.

When I try running Terminal with Rosetta 2 and install python 3.6.5, using above methods, I get the following, or some other compilation error:

Error: Cannot install in Homebrew under Rosetta 2 in ARM default prefix (/opt/homebrew)!

Finally, I downlaoded dmg file of Python 3.6.5 and installed it. It installed fine and it is visible as a python3 installation at /usr/local/bin/python3 but it cannot run.

kxxxr@Kxxxns-MBP bin % where python3
/opt/homebrew/bin/python3
/Library/Frameworks/Python.framework/Versions/3.6/bin/python3
/opt/homebrew/bin/python3
/usr/local/bin/python3
/usr/bin/python3
kxxxr@Kxxxns-MBP bin % /opt/homebrew/bin/python3 --version
Python 3.9.1
kxxxr@Kxxxns-MBP bin % /usr/local/bin/python3 --version
zsh: killed     /usr/local/bin/python3 --version
kxxxr@Kxxxns-MBP bin % 

Idle installed by Python dmg file cannot run either (I have admin rights).

Lastly came across this python bug report, which says bug is being fixed for Python 3.8, 3.9 and 3.10. Clearly, it looks like older version will not be supported on M1 chips officially.

My question is:

1. Is there other way to work with Python 3.6.5 on Mac M1? Am I missing anything?
2. If not, then please mention that. I will accept that as answer.

Thanks in advance.

Answer

Nix installed under Rosetta 2 will do the trick. I didn’t even have it installed before running the below — note the message showing Nix downloading Python 3.6 when I requested it.

# yes, this really is a M1 Mac
charles@macbook-pro ~ % uname -a
Darwin macbook-pro.lan 20.2.0 Darwin Kernel Version 20.2.0: Wed Dec  2 20:40:21 PST 2020; root:xnu-7195.60.75~1/RELEASE_ARM64_T8101 x86_64 i386 MacBookPro17,1 Darwin
charles@macbook-pro ~ % arch
arm64

# ...however, Rosetta was used to install an x86_64 Nix build
charles@macbook-pro ~ % file "$(realpath "$(command -v nix)")"
/nix/store/104sp9zrhmh3jycj32jcyl3f13mysdki-nix-2.3.9/bin/nix: Mach-O 64-bit executable x86_64

# ...and that x86_64 Nix build can install and run an x86_64 Python 3.6
charles@macbook-pro ~ % nix run nixpkgs.python36 -c python
[1 copied (53.7 MiB), 9.3 MiB DL]
Python 3.6.12 (default, Dec 18 2020, 15:32:50) 
[GCC 4.2.1 Compatible Clang 7.1.0 (tags/RELEASE_710/final)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 

The above (for reproducibility purposes) was collected with nixpkgs referring to the channel https://nixos.org/channels/nixpkgs-20.09-darwin, and specifically to the instance sn5ycj9wkbdmyinvqyg9rn42sw71wqad-nixpkgs-20.09pre245572.f18fbc33930.