error installing psycopg2, library not found for -lssl

Question

For anyone looking for a solution for this on macOS Sierra 10.12 (or later, most likely): I fixed this by installing the command line tools:

xcode-select --install

After that, pip install psycopg2 should work.

If it doesn't, you could also try to link against brew's openssl:

env LDFLAGS="-I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib" pip install psycopg2

with openssl installed via brew. Note that the brew link openssl --force does not work anymore:

$ brew link openssl --force                                                                                 17.5s
Warning: Refusing to link: openssl
Linking keg-only openssl means you may end up linking against the insecure,
deprecated system OpenSSL while using the headers from Homebrew's openssl.
Instead, pass the full include/library paths to your compiler e.g.:
  -I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib

As @macho points out below if this still does not work, you might need to use the --no-cache option of pip, e.g.

env LDFLAGS="-I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib" pip --no-cache install psycopg2

Remember to adjust these paths accordingly should you for instance build on ARM/Apple M1 Macs (as homebrew is installed at /opt/homebrew/); command as follows:

env LDFLAGS="-I/opt/homebrew/opt/openssl/include -L/opt/homebrew/opt/openssl/lib" pip --no-cache install psycopg2

I had OpenSSL installed from brew (brew install openssl)

The following worked for me:

export LDFLAGS="-L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/openssl/include"
pip install psycopg2

Using brew link openssl is dangerous as it might mess up your system by symlinking Homebrew's OpenSSL headers while the actual libraries will remain the system-supplied ones, causing all kinds of issues. Homebrew actually warns you against this if you try (and other answers suggest linking won't solve the problem anymore anyway):

$ brew link openssl
Warning: Refusing to link: openssl
Linking keg-only openssl means you may end up linking against the insecure,
deprecated system OpenSSL while using the headers from Homebrew's openssl.
Instead, pass the full include/library paths to your compiler e.g.:
  -I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib

Following this advice here's the pip command you need to use:

$ pip install -r requirements.txt --global-option=build_ext --global-option="-I/usr/local/opt/openssl/include" --global-option="-L/usr/local/opt/openssl/lib"

For pipenv, I am not aware of any command-line attributes you can pass to it, however you can export the aforementioned paths as environment variables prior to running pipenv install:

$ export LDFLAGS="-L/usr/local/opt/openssl/lib" export CPPFLAGS="-I/usr/local/opt/openssl/include"
$ pipenv install

With MacOS Catalina 10.15.4, the following was the only command that worked for me:

env LDFLAGS="-I/usr/local/opt/openssl/include -L/usr/local/opt/openssl/lib" pip install psycopg2

What worked for me was the hint provided in the command to link openssl,

$ brew link openssl
Warning: Refusing to link macOS-provided software: openssl
If you need to have openssl first in your PATH run:
  echo 'export PATH="/usr/local/opt/openssl/bin:$PATH"' >> ~/.zshrc

For compilers to find openssl you may need to set:
  export LDFLAGS="-L/usr/local/opt/openssl/lib"
  export CPPFLAGS="-I/usr/local/opt/openssl/include"

$ export LDFLAGS="-L/usr/local/opt/openssl/lib"
$ export CPPFLAGS="-I/usr/local/opt/openssl/include"

$ pip install psycopg2
Collecting psycopg2
  Using cached https://files.pythonhosted.org/packages/23/7e/93c325482c328619870b6cd09370f6dbe1148283daca65115cd63642e60f/psycopg2-2.8.2.tar.gz
Installing collected packages: psycopg2
  Running setup.py install for psycopg2 ... done
Successfully installed psycopg2-2.8.2

On mojave I added these to the .bash_profile

export PATH="/usr/local/opt/openssl/bin:$PATH"
export LDFLAGS="-L/usr/local/opt/curl/lib -L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/curl/include -I/user/local/opt/openssl/include"

was then able to install psycopg 2.8.3 in a python 3.7.4 virtualenv.

This after reinstalling xcode and the command line tools.

All the answers above helped!

This's the problem of new macOs version, where pip cannot install cryptography. What fixed my problem is to provide the env to the install command:

brew install openssl
env LDFLAGS="-L$(brew --prefix openssl)/lib" CFLAGS="-I$(brew --prefix openssl)/include" <YOUR COMMAND HERE>

You can replace <YOUR COMMAND HERE> with pip install cryptography, or pip install <SOMETHING THAT REQUIRES cryptography> for example.

Credit to this article: Fixing macOS Sierra fatal error: 'openssl/opensslv.h' or 'openssl/aes.h' file not found