Python: No Module named Zlib, Mac OS X El Capitan 10.11.6

My solution on Mojave (10.14), simply by creating symbolic link. Please take note your zlib and python version may vary.

In terminal run the following:-

brew install zlib

ln -s /usr/local/Cellar/zlib/1.2.11/include/* /usr/local/include

ln -s /usr/local/Cellar/zlib/1.2.11/lib/* /usr/local/lib

brew reinstall python

Installing the MacOS SDK Headers as suggested by this issue solves this problem fairly cleanly.

To do so, run the following (for MacOS 10.14):

xcode-select --install
sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /

and then brew install python

I had the same issue and the solution at https://github.com/Homebrew/homebrew-core/issues/29176 worked for me: re-install python@2:

brew reinstall python@2

(Before I tried this I also tried installing zlib with Homebrew -- brew install zlib; this may or may not have contributed to it working.)