Problems installing python 3.6 with pyenv on Mac OS Big Sur

Thanks to jordanm,
The solution was to follow https://github.com/pyenv/pyenv/issues/1740#issuecomment-738749988

brew reinstall zlib bzip2

From people’s comments (thanks to Lukasz Czerwinski and Alex Veksler) it seems many view this next step as optional (and even dangerous) and prefer to skip it; though, it’s worth a try if nothing else is working:

sudo rm -rf /Library/Developer/CommandLineTools
xcode-select --install

Whether you chose to skip the last step or not, continue by editing .zshrc or .bashrc using:

nano ~/.zshrc or nano ~/.bashrc

and add:

export PATH="$HOME/.pyenv/bin:$PATH"
export PATH="/usr/local/bin:$PATH"

eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"
export LDFLAGS="-L/usr/local/opt/zlib/lib -L/usr/local/opt/bzip2/lib"
export CPPFLAGS="-I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include"

after editing and saving that file, run:

. ~/.zshrc or . ~/.bashrc

Then run the command below to install (changing 3.6.0 for the desired patch)

CFLAGS="-I$(brew --prefix openssl)/include -I$(brew --prefix bzip2)/include -I$(brew --prefix readline)/include -I$(xcrun --show-sdk-path)/usr/include" LDFLAGS="-L$(brew --prefix openssl)/lib -L$(brew --prefix readline)/lib -L$(brew --prefix zlib)/lib -L$(brew --prefix bzip2)/lib" pyenv install --patch 3.6.0 < <(curl -sSL https://github.com/python/cpython/commit/8ea6353.patch\?full_index\=1)

According to this: https://github.com/pyenv/pyenv/issues/1737#issuecomment-731672292 this is related to a commit issue and the following fixes it. It worked for me.

CFLAGS="-I$(brew --prefix openssl)/include -I$(brew --prefix bzip2)/include -I$(brew --prefix readline)/include -I$(xcrun --show-sdk-path)/usr/include" 

LDFLAGS="-L$(brew --prefix openssl)/lib -L$(brew --prefix readline)/lib -L$(brew --prefix zlib)/lib -L$(brew --prefix bzip2)/lib"

pyenv install --patch 3.6.13 < <(curl -sSL https://github.com/python/cpython/commit/8ea6353.patch\?full_index\=1)

The following steps finally worked for my MacBook Air M1 with Big Sur 11.6.

‼️ Please note that this instruction is for Rosetta 2 emulated x86 terminal.

1. Install brew:

   arch -x86_64 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
   

2. Install the recommended dependencies:

   arch -x86_64 brew install openssl readline sqlite3 xz zlib
   

3. Install Pyenv with brew:

   arch -x86_64 brew install pyenv
   

4. Configure your shell’s environment (in my case zsh):

   echo 'eval "$(/usr/local/bin/brew shellenv)"' >> ~/.zshrc
   

5. Restart the terminal.

6. Add environment variables (in my case the problem was with zlib and openssl):

   export LDFLAGS="-L/usr/local/opt/zlib/lib"
   export CPPFLAGS="-I/usr/local/opt/zlib/include"
   export LDFLAGS="-L/usr/local/opt/[email protected]/lib"
   export CPPFLAGS="-I/usr/local/opt/[email protected]/include"
   

7. Install the required Python version with patch:

   arch -x86_64 pyenv install --patch 3.6.15 <<(curl -sSL https://github.com/python/cpython/commit/8ea6353.patch\?full_index\=1)
   

8. Switch shell to new Python version:

   pyenv shell 3.6.15
   

9. Check the currently used Python version:

   pyenv which python3
   

The answer by Jacob Anderson was right, but it’s worth noting that there’s no need to perform the dangerous step:

sudo rm -rf /Library/Developer/CommandLineTools 

Things worked for me (installed Python 3.6.0 on MacOS 11.4) without doing it. Thanks to Jacob!