Question

I want to get MySQL working with the system Python 2.7 in Mac OS X Lion.

I know there are a lot of questions very similar to this out there, and in fact my symptom is identical to mysql-python installation problems (on mac os x lion). However, that answer doesn’t seem to apply to my case.

My Mac is a current MacBook Pro running the 64-bit kernel:

% uname -a 
Darwin Leos-MacBook-Pro.local 11.2.0 Darwin Kernel Version 11.2.0: Tue Aug  9 20:54:00 PDT 2011; root:xnu-1699.24.8~1/RELEASE_X86_64 x86_64

The stock python on Lion is a fat binary:

% file /usr/bin/python
/usr/bin/python: Mach-O universal binary with 2 architectures
/usr/bin/python (for architecture x86_64):  Mach-O 64-bit executable x86_64
/usr/bin/python (for architecture i386):    Mach-O executable i386

I had used Migration Assistant so my system had an old installation of MySQL on it. I used the instructions at How to remove installation of MySQL on Mac OS X to remove the old MySQL installation.

MySQL 64-bit 5.5.19 was installed from the .dmg on the MySQL site. As usual, this placed the client library in /usr/local/mysql/lib. The client library appears to be exactly what we want:

% file /usr/local/mysql/lib/libmysqlclient.18.dylib
/usr/local/mysql/lib/libmysqlclient.18.dylib: Mach-O 64-bit dynamically linked shared library x86_64

However, that shared library can’t be loaded into python (I’m using the arch command to make absolutely sure I’m running the 64-bit image although the result is the same with or without that):

% arch -x86_64 python
Python 2.7.1 (r271:86832, Jul 31 2011, 19:30:53) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import cdll
>>> cdll.LoadLibrary("/usr/local/mysql/lib/libmysqlclient.18.dylib")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 431, in LoadLibrary
    return self._dlltype(name)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ctypes/__init__.py", line 353, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: dlopen(/usr/local/mysql/lib/libmysqlclient.18.dylib, 6): no suitable image found.      Did find:
    /usr/local/mysql/lib//libmysqlclient.18.dylib: mach-o, but wrong architecture
    /usr/local/mysql/lib/libmysqlclient.18.dylib: mach-o, but wrong architecture

I can reproduce this problem many other ways, notably by using the standard import MySQLdb; I’m showing the ctypes way of reproducing the bug specifically because I was trying to figure out whether the problem was in mysql-python or in the MySQL client library. From the above, it seems to be the client library. However, I’m baffled as to why the loader thinks the client library is the wrong architecture.

In trying to see whether it’s some dependent library that’s the problem, I checked the dependencies in libmysqlclient.18.dylib:

% otool -L /usr/local/mysql/lib/libmysqlclient.18.dylib
/usr/local/mysql/lib/libmysqlclient.18.dylib:
libmysqlclient.18.dylib (compatibility version 18.0.0, current version 18.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.0.1)

And of course /usr/lib/libSystemB.dylib is a fat binary as expected:

% file /usr/lib/libSystem.B.dylib 
/usr/lib/libSystem.B.dylib: Mach-O universal binary with 2 architectures
/usr/lib/libSystem.B.dylib (for architecture x86_64):   Mach-O 64-bit dynamically linked shared library x86_64
/usr/lib/libSystem.B.dylib (for architecture i386): Mach-O dynamically linked shared library i386

So… Python is 64-bit, the mysqlclient library is 64-bit, and the dependent libraries are all 64-bit… Any guesses as to why the loader is refusing the import the library would be very welcome.

Just for the belt-and-suspenders checking that everything’s 64-bit-y:

% python -c 'import platform; print platform.platform()'
Darwin-11.2.0-x86_64-i386-64bit
% ls -l /usr/local/mysql
lrwxr-xr-x  1 root  wheel  27 Dec 10 16:52 /usr/local/mysql@ -> mysql-5.5.19-osx10.6-x86_64

At this point, since I need to actually get some work done, I’m going to try switching to pymysql. This is mostly for use with Django, for which there’s a convenient way to swap pymysql in documented at the bottom of this thread.

P.S. I understand macports and can’t use it on this system.

Answer 1

Chances are you have set the default execution mode of the Apple-supplied Python to 32-bits, either by using defaults or by setting the VERSIONER_PYTHON_PREFER_32_BIT environment variable; see man python for details. In OS X 10.6 and 10.7 /usr/bin/python is an Apple-supplied wrapper program that determines which Python to run and in which mode. Using arch to execute /usr/bin/python will not influence the interpreter. For example:

$ unset VERSIONER_PYTHON_PREFER_32_BIT 
$ arch -x86_64 /usr/bin/python -c "import sys;print(sys.maxsize)"
9223372036854775807
$ export VERSIONER_PYTHON_PREFER_32_BIT=yes
$ arch -x86_64 /usr/bin/python -c "import sys;print(sys.maxsize)"
2147483647
#
# But avoiding the wrapper program ....
#
$ arch -x86_64 /usr/bin/python2.7 -c "import sys;print(sys.maxsize)"
9223372036854775807
$ arch -i386 /usr/bin/python2.7 -c "import sys;print(sys.maxsize)"
2147483647