Unable to import opengl.gl in python on macos

问题

I am using OpenGL to render a scene in python. My code works perfectly fine on windows but, for some reason, I'm having issues when importing opengl.gl on MacOS.

The issue arises when calling from OpenGL.GL import ... in both python scripts and the python console.

More specifically here is the exact call in my script:

from OpenGL.GL import glGenBuffers, glBindBuffer, glBufferData, \
    glGenVertexArrays, glBindVertexArray, glEnableVertexAttribArray, glVertexAttribPointer, \
    glDrawArrays, glUseProgram, glEnable, glDisable, \
    GL_ARRAY_BUFFER, GL_STATIC_DRAW, GL_DEPTH_TEST, \
    GL_FLOAT, GL_FALSE, \
    GL_TRIANGLES, GL_LINES, GL_LINE_STRIP

This results in the following error:

       Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/darwin.py", line 35, in GL
    return ctypesloader.loadLibrary(
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/ctypesloader.py", line 36, in loadLibrary
    return _loadLibraryWindows(dllType, name, mode)
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/ctypesloader.py", line 89, in _loadLibraryWindows
    return dllType( name, mode )
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ctypes/__init__.py", line 373, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: ('dlopen(OpenGL, 10): image not found', 'OpenGL', None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/iyadboustany/Desktop/lensmaster/Lensmaster.py", line 18, in <module>
    from MainWindow import MainWindow
  File "/Users/iyadboustany/Desktop/lensmaster/MainWindow.py", line 14, in <module>
    from Robot import Robot
  File "/Users/iyadboustany/Desktop/lensmaster/Robot.py", line 8, in <module>
    from Graphics.Scene import DHNode
  File "/Users/iyadboustany/Desktop/lensmaster/Graphics/Scene.py", line 13, in <module>
    from OpenGL.GL import glGenBuffers, glBindBuffer, glBufferData, \
  File "/usr/local/lib/python3.8/site-packages/OpenGL/GL/__init__.py", line 3, in <module>
    from OpenGL import error as _error
  File "/usr/local/lib/python3.8/site-packages/OpenGL/error.py", line 12, in <module>
    from OpenGL import platform, _configflags
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/__init__.py", line 36, in <module>
    _load()
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/__init__.py", line 33, in _load
    plugin.install(globals())
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/baseplatform.py", line 97, in install
    namespace[ name ] = getattr(self,name,None)
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/baseplatform.py", line 15, in __get__
    value = self.fget( obj )
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/darwin.py", line 62, in GetCurrentContext
    return self.CGL.CGLGetCurrentContext 
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/baseplatform.py", line 15, in __get__
    value = self.fget( obj )
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/darwin.py", line 45, in CGL
    def CGL(self): return self.GL
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/baseplatform.py", line 15, in __get__
    value = self.fget( obj )
  File "/usr/local/lib/python3.8/site-packages/OpenGL/platform/darwin.py", line 41, in GL
    raise ImportError("Unable to load OpenGL library", *err.args)
ImportError: ('Unable to load OpenGL library', 'dlopen(OpenGL, 10): image not found', 'OpenGL', None)

Notes:

• Running glxgears works just fine.
• I'm running macOS Big Sur beta (20A5343i)
• I'm using python 3.8.5
• I installed opengl using pip: pip3 install PyOpenGL PyOpenGL_accelerate

回答1:

This error is because Big Sur no longer has the OpenGL library nor other system libraries in standard locations in the file system and instead uses a cache. PyOpenGL uses ctypes to try to locate the OpenGL library and it fails to find it. Fixing ctypes in Python so that it will find the library is the subject of this pull request

https://github.com/python/cpython/pull/21241

So a future version of Python should resolve the problem.

To fix it now you can edit PyOpenGL file OpenGL/platform/ctypesloader.py changing line

    fullName = util.find_library( name )

to

    fullName = '/System/Library/Frameworks/OpenGL.framework/OpenGL'

回答2:

Since I hate the idea of patching a Python package (plus it is really hard to manage that with use of Conda to install said package), I offer this kludge as a workaround for until Python gets its Big Sur (aka Big Nuisance) update:

try:
    import OpenGL as ogl
    try:
        import OpenGL.GL   # this fails in <=2020 versions of Python on OS X 11.x
    except ImportError:
        print('Drat, patching for Big Sur')
        from ctypes import util
        orig_util_find_library = util.find_library
        def new_util_find_library( name ):
            res = orig_util_find_library( name )
            if res: return res
            return '/System/Library/Frameworks/'+name+'.framework/'+name
        util.find_library = new_util_find_library
except ImportError:
    pass

回答3:

It's better to change this to

fullName = "/System/Library/Frameworks/{}.framework/{}".format(name,name)

otherwise GLUT won't work. At least, this let me run the Cozmo SDK's 3d stuff again.

来源：https://stackoverflow.com/questions/63475461/unable-to-import-opengl-gl-in-python-on-macos