在OS X上，是否可以从纯Python获取用户库目录？

Question

我正在编写一个纯Python库，出于各种原因，我非常想避免要求用户安装任何二进制扩展名。 但是，在OS X上运行时，我也想找到用户库目录（ ~/Library ），以便在其中存储一些配置数据，我的理解是，对于“非常有效且含糊但重要的原因”，正确的做法是这不仅仅是通过在我的代码中编写~/Library ，而是通过询问OS X目录中包含一些代码的地方，例如

[NSSearchPathForDirectoriesInDomains(NSLibraryDirectory,
                                     NSUserDomainMask,
                                     YES)
 objectAtIndex:0];

当然，此代码是Objective-C，而不是Python，因此我不能直接使用它。 如果它是纯C语言，我只会使用ctypes从Python调用它，但事实并非如此。 有什么方法可以从Python进行此调用，而无需在Objective-C中编写扩展模块或要求用户安装某些扩展模块（如PyObjC ？ 或者，如果我像其他所有人一样放弃并硬编码~/Library ，那么会发生什么可怕的事情吗？

Answer 1

好吧， 它是底层的普通C语言，因此您可以使用ctypes模块获得相同的结果：

from ctypes import *

NSLibraryDirectory = 5
NSUserDomainMask = 1

def NSSearchPathForDirectoriesInDomains(directory, domainMask, expand = True):
    # If library path looks like framework, OS X will search $DYLD_FRAMEWORK_PATHs automatically
    # There's no need to specify full path (/System/Library/Frameworks/...)
    Foundation = cdll.LoadLibrary("Foundation.framework/Foundation")
    CoreFoundation = cdll.LoadLibrary("CoreFoundation.framework/CoreFoundation");

    _NSSearchPathForDirectoriesInDomains = Foundation.NSSearchPathForDirectoriesInDomains
    _NSSearchPathForDirectoriesInDomains.argtypes = [ c_uint, c_uint, c_bool ]
    _NSSearchPathForDirectoriesInDomains.restype = c_void_p

    _CFRelease = CoreFoundation.CFRelease
    _CFRelease.argtypes = [ c_void_p ]

    _CFArrayGetCount = CoreFoundation.CFArrayGetCount
    _CFArrayGetCount.argtypes = [ c_void_p ]
    _CFArrayGetCount.restype = c_uint

    _CFArrayGetValueAtIndex = CoreFoundation.CFArrayGetValueAtIndex
    _CFArrayGetValueAtIndex.argtypes = [ c_void_p, c_uint ]
    _CFArrayGetValueAtIndex.restype = c_void_p

    _CFStringGetCString = CoreFoundation.CFStringGetCString
    _CFStringGetCString.argtypes = [ c_void_p, c_char_p, c_uint, c_uint ]
    _CFStringGetCString.restype = c_bool

    kCFStringEncodingUTF8 = 0x08000100

    # MAX_PATH on POSIX is usually 4096, so it should be enough
    # It might be determined dynamically, but don't bother for now
    MAX_PATH = 4096

    result = []

    paths = _NSSearchPathForDirectoriesInDomains(directory, domainMask, expand)

    # CFArrayGetCount will crash if argument is NULL
    # Even though NSSearchPathForDirectoriesInDomains never returns null, we'd better check it
    if paths:
        for i in range(0, _CFArrayGetCount(paths)):
            path = _CFArrayGetValueAtIndex(paths, i)

            buff = create_string_buffer(MAX_PATH)
            if _CFStringGetCString(path, buff, sizeof(buff), kCFStringEncodingUTF8):
                result.append(buff.raw.decode('utf-8').rstrip('\0'))
            del buff

        _CFRelease(paths)

    return result

print NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask)

但是如果只使用~/Library ，宇宙可能不会崩溃。