Mac OS X Lion Psycopg2: Symbol not found: _PQbackendPID

I recently upgraded to Mac OS X Lion and am trying to get psycopg2 working again with python 2.6. The instructions on previous sites to force Python to run in 32 bit more (seen places like here: http://favosdream.blogspot.com/2009/09/make-psycopg2-and-readline-work-in-snow.html ) aren't giving any luck. Even trying to force python to 32 bit using arch -i386 python is still giv开发者_高级运维ing me the error:

symbol not found: _PQbackendPID
  Referenced from: /Library/Python/2.6/site-packages/psycopg2/_psycopg.so
  Expected in: flat namespace

Recently had this issue trying to import psycopg2 (2.8.2) into a python3 (3.5.3) project. Running macOS Sierra (10.12.6), using PostgreSQL 9.6 + pgAdmin3.

TLDR: be careful when installing SQL programs & the dynamic links that installers create

From what I can tell, the required libpq dynamic library (libpq.5.dylib) that's compatible with psycopg2 (2.8.2) is libpq 5.9+ (libpq.5.9.dylib)

When postgres (or other postgres-dependent programs) are installed, they may create dynamic links in /usr/lib to the newly installed .dylib files, which may not necessarily be the ones you want.

For example, /usr/lib/libpq.5.dylib may point to ./Applications/pgAdmin3.app/Contents/Frameworks/libpq.5.dylib, which is version 5.6; the older version of the libpq dynamic library may not include some functions, like _PQsslAttribute, in this case.

The solution that worked for me:

Move /usr/local/lib up in $PATH (since usr/lib may only be writable by root), then create a dynamic link in /usr/local/lib to point to /Library/PostgreSQL/9.6/lib/libpq.5.9.dylib like this:

cd /usr/local/lib
ln -s /Library/PostgreSQL/9.6/lib/libpq.5.9.dylib ./libpq.5.dylib

I had this problem too on Snow Leopard/10.6.8, and just lost a half a day in the middle of a pretty intense contract. Not fun. I ended up fixing it by a) fully removing all postgres versions and rebooting, b) fully removing all my psycopg2 installs (use locate and be ruthless), c) upgrading my system python to 2.7, d) reinstalling virtualenv and pip so they pointed at the right python version, and then e) following the instructions on this page, starting with install postgres 9.1 from the dmg installer:

http://hardlifeofapo.com/psycopg2-and-postgresql-9-1-on-snow-leopard/

Ultimately it was this easy:

virtualenv your_virtual_env_name
. your_virtual_env_name/bin/activate
export ARCHFLAGS="-arch i386 -arch x86_64"
export PATH=$PATH:/Library/PostgreSQL/9.1/bin
pip install psycopg2

Good luck!

Did you try arch -i386 python2.6 if you are using the Apple-supplied Python 2.6 in /usr/bin/python2.6? But if you are still running a 32-bit version of psycopg2 and the PostgreSQL client libraries, it might be a good time to install newer 64-bit or 64-bit/32-bit universal versions. MacPorts can help with that.

Symbol not found: _PQbackendPID Expected in: flat namespace

I have come across the same symbol error on Arm64 Mac with Big Sur.

I am using Progressapp (x86_64) and psycopg2 v2.8.4 (Arm64). Since Progressapp Arm64 version is not yet available I decided to check the linking of the libraries for psycopg2.

My solution was, first to uninstall Progressapp, then export PATH=/opt/local/lib/postgresql13/bin:$PATH point to Arm64 libpq.5.13.dylib, and finally re-install Pogressapp. So psycopg2 loads all Arm64 libraries needed.

otool -E venv/lib/python3.8/site-packages/psycopg2/_psycopg.cpython-38-darwin.so outputs:

    /opt/local/lib/postgresql13/libpq.5.dylib (compatibility version 5.0.0, current version 5.13.0)
        /opt/local/lib/libssl.1.1.dylib (compatibility version 1.1.0, current version 1.1.0)
        /opt/local/lib/libcrypto.1.1.dylib (compatibility version 1.1.0, current version 1.1.0)
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1292.60.1)