Pyenv won't install python 3 on Mac os 11

Question

Trying to install Python 3.9.0 on Mac OS 11.0.1 with pyenv install 3.9.0.

Results:

python-build: use readline from homebrew
Downloading Python-3.9.0.tar.xz...
-> https://www.python.org/ftp/python/3.9.0/Python-3.9.0.tar.xz
Installing Python-3.9.0...
python-build: use readline from homebrew
python-build: use zlib from xcode sdk

BUILD FAILED (OS X 11.0.1 using python-build 20180424)

Inspect or clean up the working tree at /var/folders/n6/q2b78971589bltfczw539flh0000gn/T/python-build.20201114175722.7103
Results logged to /var/folders/n6/q2b78971589bltfczw539flh0000gn/T/python-build.20201114175722.7103.log

Last 10 log lines:
checking for python3... python3
checking for --enable-universalsdk... no
checking for --with-universal-archs... no
checking MACHDEP... "darwin"
checking for gcc... clang
checking whether the C compiler works... no
configure: error: in `/var/folders/n6/q2b78971589bltfczw539flh0000gn/T/python-build.20201114175722.7103/Python-3.9.0':
configure: error: C compiler cannot create executables
See `config.log' for more details
make: *** No targets specified and no makefile found.  Stop.

Many suggestions in similar questions seem to revolve around XCode, but xcode-select --install says command line tools already installed.

Any help appreciated.

Answer 1

I ran into the same issue today and managed to get one step further after diving into the config.log and checking this post here.

I had to take the opposite direction and execute sudo xcode-select --switch /Applications/Xcode.app/ after downloading Xcode from the App Store. If you run clang --version it should show Apple clang version 12.0.0 (clang-1200.0.32.27).

I was able to execute pyenv install 3.9.0 and get past the C compiler cannot create executables error, but unfortunately it still failed. config.log is huge this time around, will see if I can find anything.

EDIT: I managed to install 3.8.0 by executing the following command including a patch found here.

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

There have been some macOS 11.0 merges, but I assume the repos used for the pyenv install command are simply not yet updated. This workaround will suffice for my needs for now, however.