Can't install psycopg2 package through pip install on MacOS

I am working on a project for one of my lectures and I need to download the package psycopg2 in order to work with the postgresql database in use. Unfortunately, when I try to pip install psycopg2 the following error pops up:

ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command '/usr/bin/clang' failed with exit status 1
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command '/usr/bin/clang' failed with exit status 1

Does anyone know why this is happening? Thanks in advance!

I fixed this by installing Command Line Tools

xcode-select --install

then installing openssl via Homebrew and manually linking my homebrew-installed openssl to pip:

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

on macOS Sierra 10.12.1

Try installing it with:

pip install psycopg2-binary

brew install postgresql

If postgresql exist then run:

brew upgrade postgresql
sudo pip install psycopg2

In venv:

env LDFLAGS='-L/usr/local/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/readline/lib' pip install psycopg2==2.8.4

If you need use only the command pip install psycopg2 export the path in macOSX:

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