Mac OS X Lion Python Ctype CDLL error lib.so.6 : image not found

Question

I am a beginner in Python. When I tried the following Python sample code with type library on Mac OS X Lion:

#hello.py
from ctypes import *
cdll.LoadLibrary("libc.so.6")
libc = CDLL("libc.so.6")
message_string = "Hello World! Hello Python!\n"
libc.printf("Testing :%s",message_string)
//

An error occurred as following:

Traceback (most recent call last):
File "cprintf.py", line 2, in <module>
cdll.LoadLibrary("libc.so.6")
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(libc.so.6, 6): image not found

Can anyone tell me what's the matter? BTW, I tried this on Windows and Linux; it worked well. Need I make some configuration for ctype.

Thanks very much,

Ricky

Answer 1

A cross platform solution would be to use something like this:

import platform
import ctypes

libc = ctypes.cdll.LoadLibrary("libc.{}".format("so.6" if platform.uname()[0] != "Darwin" else "dylib"))
# or ctypes.CDLL("libc.{}".format("so.6" if platform.uname()[0] != "Darwin" else "dylib"))

Not quite sure what the difference is between these alternatives, as both seem to work nicely!

Answer 2

Shared libraries on Mac OS X tend to have the extension .dylib instead of .so. In this case, /usr/lib/libc.dylib is what you want so load libc.dylib.

Answer 3

OS X uses ".dylib" for the extension of its shared objects, so you need to use "libc.dylib" instead.